Note: You need a bookshelf and you might lose the books you have purchased from the book store.

Step 1
Buy the cheapest bookshelf there is, if you don't already have one.

Step 2
Click on the bookshelf and select browse.

Step 3
Sell one of the books then go to buy mode.

Step 4
Click on your bookshelf and sell it and then click the redo button and go back into sim mode. This will double the amount of books in your bookshelf.

Step 5
Repeat Steps 3 and 4 until you have 100 or even 1000 of each book type in your bookshelf.

Step 6
Click browse and sell all of those books.