Scrying is a magical technique, demonstrated by Abel in strip #654, which allows the user of the spell to quickly skim through a book and rapidly absorb all information contained within it. Quoting Amber from her post on scrying,

As many have noticed, Abel did a "scry" on the book...which is the equivalent of a super-speed read. This has its advantages and disadvantages as I will explain.

On the plus side, it lets you study something REALLY fast and really intense in a matter of seconds. Handy for tests or where you need to recite a particular spell syllable for syllable.

However, it tends to be only temporary as what it does is it basically crams all that knowledge into your short term memory spot. So after a day or so it will fade, and by a week you likely will have forgotten it all. While there are alternate versions that last longer and are more permanent...they require more skill obviously.

As mentioned, it also takes a bit of the enjoyment out of reading and most creatures given the time would prefer to sit and read. In such a case, one can emply a stronger spell which would enable them to remember the contents far more accurately and permanently.

The scry is a bane of many bookstores as some sneakier creatures like to scry a book, then quickly regurgitate the information into a copy for later consumption.(ew...that sounds gross)

Another big drawback to the scry is it takes a lot of space in the short-term memory and thus other things get pushed out...leaving the user somewhat absentminded in the short-term memory department save for the information they scribed. Good for last-minute tests...but bad if you also made a plan ten minutes prior to meet someone at a particular place after the test. Many a student has lost a date due to them scrying before a test then forgetting to pick up their partner afterwards until the next day.

And obviously, the bigger the book, the more one has to scry, and the more one has to push out of their short term. With practice the side effects can be minimized though.

Apparently, some bookstores have restrictions on scrying, as shown in strip #654.