I like to read books of many different genres including Atheism themed books. I’ve purchased several Atheism themed books on Amazon for my Kindle. I haven’t read all of them yet, but I’ve purchased several. You may not realize this but there are many, many books on Amazon for free or for $0.99. That’s much cheaper than the $7.99 or $9.99 that is typical of books written by more well-known authors in the area. To find these books, just go to Amazon, type in ‘Atheist’ or ‘Atheism’ in the search bar of the Kindle store and voila! Change the list rankings from low to high price and the free books will appear first. Here’s the link to what pops up for me when I do a search.
I can’t comment on the quality of all of these free books, but several are quite good. Be a bit careful as there are a few religious books attacking Atheism that appear on this list. You can certainly read these as it is always good to hear what the other side has to say, but if that’s not what you’re looking for, just read through the book description before downloading to double check.