I have been adding a lot of really great books to my Kindle library, and one of the main ways that I have been doing this (mostly for free) is by using Bookbub.com and Bookgorilla.com . Both work in about the same way, but it seems to me that Book Gorilla offers more books, and a better selection choice than Bookbub does. The way it works, is that you make an account with either service (or both), and then you can select the type of books that you are interested in, and each day they will send you an email showing free and cheap (usually under $3) books that fit your categories. Since Amazon always puts some of their books on sale for free each day to promote that book, and then they go back to the regular price, you can also find free books by going to the Amazon webpage and searching the Kindle Store for free books in those categories . However, if you do not remember to check every day, you can miss good books that were only free for a day or two; and this is where a service like Book Gorilla can help out. I have mine set to show me gardening books, health books, and recipe books, as well as fiction that I enjoy reading for entertainment. Once I get the book in my Kindle library, then I add it to a “collection”. You can set up a collection for any kind of book that you want, and then add more books to the collection. As an example, one collection might be Garening Books. Then, every time you get a free gardening book download from Kindle, you can add it to the gardening collection, so when you want to read about gardening, you do not have to look through your whole Kindle library, you just look in your gardening collection. Except for books that I am currently reading, I store most of the library books in the Amazon Cloud, so I am not even loading up my Kindle with a lot of books, and you can pretty well store unlimited books in the cloud. To use either of these book-finding services, just go to their respective website, register for an account (which is free) and then select the categories of books you want to read.