You may need to value your books for insurance purposes, or if you are deciding whether to sell or donate to your library. The Internal Revenue Service (IRS) allows you to deduct the value of any books you donate to charity, but you need to show that you have tried to make an accurate assessment of the books' fair market value. If you own a large number of books, this can be a time consuming process, but it is worth doing as you may find your books are worth more than you think.