Can you read the books you buy, or does Geralt just absorb the knowledge automatically?

Actually, I think both. You can (and should) read the books to get the back story, but it appears that as soon as you acquire a book the information goes directly into your journal, and any side effects (such as knowledge of a type of beast) is automatically applied.

Note that, unlike formulas and diagrams, books can be sold after having been "read" without losing their information.

Thanks for the reply, but I must be dumb as I can't figure out how to read a book lol :)

Open your inventory, go to the books tab, and double-click on the book.

Thank you kindly.

You can sell them??? ( like in TW1)
thank god heh
wading through the inventory is bad enough that should improve it a bit

I think you have to double click on the book to absorb the knowledge. At least for the monster-related books you need to.

I do miss the old way of cataloging stuff. Now, I don't know whether I've read a book before, neither do I know if any book I read added info. And, on top of that, books are no longer as vital - you had to read books before to complete quests but this is no longer so.