Mount&Blade/Books

Books are purchased from the Book Vendors randomly found in taverns. No one Vendor has all the books, so you will need to visit multiple taverns if you want to collect them all. Each book has a minimum Intelligence level required to read it.

Books come in two forms. A book that states what the bonus is will grant you that bonus for as long as the book is in your inventory, and to reflect this it will be listed as a "(+1)" in the Party window. Books that list a progress percentage will only only give you a bonus after you have digested the information they contain, but once you have reached 100% the bonus is permanent and you can discard the book.

Reading books
In order to learn from percentage-based books you must have them in your inventory for the entirety of the reading session. On the world map, click the Camp button and choose "Take an action", then choose "Select a book to read". Pick a book from the menu and you will begin digesting the information it contains. You can only read one book at a time. You can change between books if you wish to, and you will keep your progress towards absorbing each book.

You can check what book you are reading by clicking on Reports and then Character report. You read about 7% of the book every three days, so it will take approximately 42 days to completely digest a book. Once this time is complete a dialog box will tell you what bonus it has granted. After this you no longer need the book in your inventory.

Available books
These prices are raw data extracted from  using the M&B Item Editor. In practise, merchants will normally charge more for books they sell and pay less for those they buy. Putting points in Trade will bring these amounts closer to the item's true value.