I'm not sure why they are free. Since they are on the limited time promotion page, it is something that Amazon has done on purpose.
I now have a complete list with links on my blog (minus one "book" that was described as a list of book titles, which even then got a one-star review for being full of shorthand). A few are short stories (some very short), a few erotica, but most appear to be fantasy, scifi, romance or thriller/horror. Quite a few are full length books and the start of a series. A couple of authors have multiple titles involved.
Since there are 58 titles (+ the one I skipped), I won't repeat them here (plus, my fingers are now officially tired and on strike).