I fairly frequently get asked how I find all of the sale and free books that I post on Bookwi.se. One of the best tools I use is ereaderiq. There are three main ways I use ereaderiq, price watch a specific book, search for free or sale books, and to notify me when a book become available on kindle.
This is the tool I use most. If you are a big user of Amazon’s Wishlist you can import your wishlist directly into ereaderiq and ereaderiq will email you when the price of a book drops. This is what I did when I initially started using ereaderiq, but now I use ereaderiq’s ‘1-click watcher‘ button. When I am on the Amazon page of a book I want, I click the button on my browser and it automatically adds the book to the ereaderiq list..
If you only want a few emails, you can set a notify threshold. If you have a $9.99 book and you want it to notify you when it drops to $7.99, you set the notify level at $2.00 and give your email address. I tend to go look at the list every couple days because I am impatient, but you do get emails. My books are mostly theology and do not move much. New Releases and Fiction tend to move more often.
I don’t use them as much, but ereaderiq also has the ability to browse for books based on current price, and subject areas. If you want to look for books that are between $2 and $3 and is young adult fiction, you can do that.
Also ereaderiq will notify you when a book has a new kindle version. You just use the one click watcher from the hardcover or paperback page and it will add it to a list of books that are waiting to be released in kindle versions.