Today I present to you a book generator based on the numbers produced by Mr. Smolensk at the Tao of D&D on his article “Books.” Now, as this is purely a list of book subjects/categories and not actual titles, you will have to make up titles and authors for any books you generate. I’m sure you can think up something if you are clever enough to enjoy worldbuilding. On to the generator and how to use it!
It’s set up on a single Google Sheet page, so you don’t have to go mucking about with any tabs or anything. Simply refresh the page to generate a new number in the “Roller” box, and look up the number on the accompanying table. Example: if you roll a 628, you want to find the number in the “Roll (up to)” column that is just over 628, which happens to be 642, Missions and Missionaries in the Religion category. Then, you will notice that the number next to the Roll (up to) column is colored. Go back up to the top, and refer to the number in the correspondingly colored box under the Rarity Table heading. This will be a random number between 1 and 100. Find the indicated percentage in the same row as the colored box, and the column heading will give you the rarity of the book you generated. See my post about the Function of a Library for more on the rarity of books (and their uses). Missions and Missionaries happens to be a blue box, so we look at the Blue box on the Rarity Table, see it is 98, and referring to the numbers in that row, we find that we have a common book about missions or missionaries.
Figuring out how much these books are worth is completely up to you, and should depend on how rare books are in general in your world, and how much value you place on the bonus to Knowledge checks they confer.
Random books can be found in treasure stashes of nobles or wizards, or you could generate the stock of a bookseller in your world. If you run across a subject that is too advanced for the technology of your world, I suggest making it a book on a similar subject, but from a magical or alchemical perspective.