The Written Word
In 1007, writing is much less important to most people than it is today. The great majority of people are illiterate; and FW characters are also likely to be illiterate. Still, writing is important to society as a whole, and books are treasured.
There is no printing; all books must be hand-written. This greatly contirbutes to their cost, and to the time and labor it takes to make one. Entire monasteries are dedicated to nothing but copying texts. Most books are beautifully illuminated works of art. Anicent learning is seen as very important; the reason so many books are copied is to preserve the teaching of the church fathers. However, secular books are also copied, so works from many ancient philosophers and poets are also preserved.
Books are mostly written in Latin. Even though Latin is not widely spoken anymore, it is still viewed as the language of learning. Vernacular languages are considered vulgar, and not generally used for written works. This, along with the microscopic literacy rate and the huge cost of books, puts a huge gulf between the average person and the written word. Most people wouldn't understand books even if someone read aloud to them!
The form of book used in 1007 is the codex; i.e., the form of book we are familar with today, with a spine, covers, pages, and the ability to open and lie flat on a table. The earlier form of book, the scroll, is no longer in general use, and hasn't been since Roman times. PCs are unlikely to ever see a scroll unless they go to a synagogue.
Writing is generally done on parchment, not paper. Parchment is made of animal skin; for example, vellum, the highest quality of parchment, is made from calfskin. In the modern era, parchment is still used for important documents like diplomas, so it may be familiar to players. Parchment, as you might guess, makes books even more expensive. Paper has appeared, and its use is increasing, but it is still considered an expensive luxury product. Christendom has not discovered the secret of papermaking, so paper must be imported from Moslem Spain. In the Islamic world, paper is much cheaper than parchment, and rapidly coming into general use.
Because books are so expensive and rare, libraries are much smaller. Even most literate people own no books. A personal library of a dozen codices is extravagant. A large university library may have hundreds of tomes (truly huge one, maybe a thousand or two); compare this to the millions of books in even modest public libraries today.