One more if you think you can catch it before the end of the day when Amazon rotates these (around 12:30 AM PST, usually).
The late William C. Anderson wrote a number of things out from Bantam, Crown, and other publishers, including several novels that were turned into Hollywood movies. Whoever's currently handling his estate returns to offer a true crime about the US' first female serial killer, originally out from small press Fred Pruett in 1994, which from experience, will probably be offered for just one day only (today, in which there's less than an hour left):
Lady Bluebeard
Also, MuseItUp Publishing, which I suspect to be some sort of division of Books We Love/BWLPP offers a new mystery/thriller freebie, alongside a romance repeat.