Lots of questions always arise on these topics, so I'm placing all this info here in one topic, to maybe help people understand how all these things can work in the game. This is mostly based on how the rules function in the Rules Cyclopedia, with lots of added fluff to explain why they work that way.
Spellcasting 101
In order to harness the magical forces of the cosmos, a magic-user must learn to imprint the magical power of a spell into his mind. This is usually referred to as "memorization," but it is actually more than simply remembering words and hand gestures to repeat later on, although that is part of what must be memorized. The more important part of memorizing a spell is actually imprinting and storing the required magical energy in your mind. This is accomplished through study of one's spellbook.
So, before a magic-user can learn to actually cast a spell, he must learn to write a spell in his spellbook, in a form that is specifically in tune with his own magical energies. Each person's magical energies, astrological signs, and mental workings are unique. No spellcaster can memorize a spell that is written by someone else, because it won't be tuned for his own magical energy. In order for a magic-user to memorize any spell, that spell must be scribed with the appropriate glyphs and symbols in the specific order to be compatible with that mage's astrological signs, star charts, numerological constants, and personal energies. This process is necessarily a bit time-consuming, because the mage must consult his stars and astrological charts, plus do a bit of experimentation with rare materials to observe the reactions to his personal energies in order to find the proper glyphs to inscribe into his spellbook.
Yes, this process is indeed a bit complex, but it is the first thing all magic-users must learn in their quest to master magic, since, as mentioned, no mage can memorize spells using another mage's spellbook. In fact, because each spell is written to be specific to a certain mage, any other mage viewing that written spell will find it to be completely incomprehensible, though use of a Read Magic spell will allow comprehension of what the written spell actually does, though this still does not allow another mage to imprint the incompatible spell formulas into his own mind.
Each mage must write his own version of a spell into a spellbook in order to enable him to cast it.
So what exactly is a spellbook then? Contrary a common misconception, spellbooks are not actually magical in themselves -- they are not magicaly enchanted items. You may think of them as "instruction manuals" that each mage must study in order to memorize a spell, made from standard non-magical (but generally high-quality) parchment and ink, like any other book. Each spell in a spellbook will generally take up a single page, because the magic-user must be able to see the entirety of the spell formulas when he is imprinting it into his mind. This is why spellbooks tend to be on the large size -- large books with large-enough pages to fully hold a single spell formula entirely and legibly.
A magic-user must stare at the magical symbols, runes, and glyphs on a page to force the magical energies they represent directly into his mind, along with noting the proper hand gestures and mystical words needed to release that energy from his mind. The magic-user must have a well-rested mind in order to receive a spell, and it requires somewhat intense concentration upon the formula written on the page, though slight interruptions in concentration will not ruin the process or memorization. To those readers not yet versed in this process, you might liken it to staring at a picture for an extended period of time until you can see that image even after you look away from the page and close your eyes... except that the properly-ordered glyphs and runes being imprinted into the mind of a spellcaster will actually semi-permanently imprint the power they contain into his mind, ready to be released at a later point. Not until the spell is fully imprinted in the mage's mind will the spell be ready to cast, and this takes some time -- around an hour. A spell simply cannot be prepared any faster than that, as it takes time to be firmly imprinted into the mage's mind and fully form the energies needed to cast it. As a magic-user becomes more capable of memorizing more numerous and more powerful spells, he will find, through experience, that he can still imprint even his maximum number of spells into his mind within an hour of study.
Let us digress a moment and touch upon how it is that a neophyte magic-user inscribes a spell formula into his spellbook. In order to develop a spell specifically in tune with his own magical energies, a magic-user can attempt to build the formula completely from scratch. Obviously this will require a lot of time, research, and costs (for rare components and reagents) in order to work out the unknown formula. For a simple spell, this process will require around a week to complete, and the mage can expect to spend around 1000 gold coins for the rare components expended in the process. Further, an untalented student might fail in his attempt, and have to start over in his research, though it would not take as long or cost as much in his second attempt, since we learn even through failure. The benefit of building your own spell from scratch is that you can not only build the formula for a common spell you have not yet mastered, but you can also create just about anything (within your power) that you can imagine, such as a brand new spell, never before seen.
However, if you are attempting to master a commonly known spell, you are better off obtaining a copy of that spell from another mage's spellbook. If you have a copy of another mage's complete spell to start your work from, this will save you time and costs when reworking the formula for your own use, since you don't have to begin completely from scratch. To transcribe a simple spell in this manner, you might expect to pay only 400 gold coins and spend a mere 4 days to work out the correct formula for yourself (though as a note, the process can be speeded up by spending more money on special components; conversely, the process can be accomplished more frugally if one takes more time and care with the use of their components -- for example, a magic-user might choose to spend 700 gold coins for extra components, intending to burn though the materials rapidly in order to complete his research in only 1 day, or he may be very careful with his components and calculations, taking a full 7 days in the process but only having to expend 100 gold coins on components). Additionally, your chance of success is improved by building upon the works of others. Though as previously noted, this will require the use of a Read Magic spell in order to comprehend the other mage's formula -- for this reason, Read Magic is almost invariably the first spell every magic-user learns (with the added benefit that mis-casting Read Magic by inexperienced students generally doesn't result in any major destruction or death).
Of course, once a magic-user has developed the formula he needs to cast a spell, he can easily make copies of that formula for himself in a backup spellbook, requiring only that care be taken to make the copy exact, with no typographical errors. Aside from some quality ink, parchment, and quills, it will generally only require about 2 hours of work to copy a single spell correctly.
So now, students, you understand the basics of spellcasting. It requires a specific magical formula worked out by a mage and written into his spellbook + the mind of that specific mage capable of absorbing that specific formula + an hour to imprint the magic power upon the mind + the releasing of that power through the proper gestures and words.
Of course, as is common knowledge, once the power is released by casting the spell, the imprinted power in your mind is obviously released in the process, so you won't be able to cast that spell again until you memorizes it once more to re-imprint that spell into your mind.
Understanding this process should also make it clear why a magic-user cannot cast spells directly from his spellbook -- it takes an hour for the magical "charge" to build up in the mind and be ready to use. Obviously, this can be inconvenient when a mage needs to cast a certain spell quickly, but he has not previously imprinted that spell into his mind.
For this reason and others, we come to the topic of magical spell scrolls.
What is a spell scroll? Basically speaking, it is a magically-enchanted vessel for spell energy, with included instructions for releasing that energy and thus allowing a magic-user to "cast the spell..." in a manner of speaking. This "casting" is not as involved as actually casting a spell from the mind, since activating a spell scroll only involves focusing on any targets or specific effects needed to control the magic, while reading the magical activation words from the parchment -- usually the same words as required for the original writer of the scroll to cast that same spell, since it is actually a stored version of his own spell. Since the magical words, glyphs, and runes on a spell scroll are written by another magic-user (in his own magical idiom), this will again require use of a Read Magic spell in order for another mage to properly comprehend them, but once so comprehended, a mage may use the spell scroll at any time in the future without further use of Read Magic.
Obviously, it is not a simple procedure to store spell energy within a scroll. Only upon reaching higher levels of ability will you be able to master the enchantment process. For now, it is sufficient to say that even the most simple of spells would require an expenditure of around 500 gold coins (for rare inks, parchment, and spell components, because when enchanting a scroll, mundane ink and parchment will simply not be able to store the spell energy), and a period of about a week in order to allow the scroll to fully absorb the enchantment. And even then, the process may fail (dependent on the skill of the mage), resulting in nothing but a worthless piece of paper.
However, one major benefit of spell scrolls (aside from having a portable, pre-charged spell ready to cast at any time), is that a magic-user can easily reverse-engineer any spell contained in a scroll, as long as he has appropriate skill to be able to cast the spell from his own mind.
Indeed, since the fully-developed magical energies -- the completed spell -- is stored within a scroll, a magic-user, rather than releasing the spell from the scroll to generate the usual spell instantly, can instead release the energy slowly into his own mind so that he can fully comprehend it, and, aided by the scroll creator's own magical phrasing, the mage will be able to easily know which glyphs, runes, and mystical symbols (and in what order) are needed for him to be able to imprint the spell into his own mind.
Since the spell energy is released into the magic-user's mind for analysis (it will not be in a proper form for him to store in his mind), this will drain the magical charge from the scroll just as if it had been cast. But during this process the mage can easily transcribe the spell formula into his own spellbook in the appropriate format for him to later memorize. This process is fairly quick, requiring only that the same care be taken as when making a direct copy of a spellbook page -- so generally around 2 hours should be needed.
I believe we have covered all the basic information you need in order to get started. Please make sure your tuition is paid in full. You may begin research right away on the Read Magic spell. The library and laboratory will be at your disposal.
Once you have mastered Read Magic, you will then be able to use it to study other spell transcriptions made by previous students to add to your spellbooks. If you show aptitude, you may be awarded some scrolls in order to speed up your acquisition of spell knowledge.
What's that, Potter? ... NO, you do not get a magic wand.... You couldn't even use it yet -- not until you master controlling magical forces in your mind through spellcasting. What? NO! Wands are NOT required for casting spells! How stupid would that be? All someone would have to do is take away your wand and you'd be completely helpless.... Plus, how would you even enchant a wand if you don't already have one, and you couldn't cast spells without one? Such nonsense. Just go learn how to do your spell research, and then no matter what happens, you will always be able to rebuild a spellbook from scratch so that you can cast spells.
Any further questions?