I'm kind of amazed no one has posted this yet - or maybe it's been posted elsewhere and I missed it - but Amazon.co.uk have yet another summer sale on of books ranging between 99p and £3, including some amazing bargains. Details here:
Kindle Summer Sale
I can particularly recommend Chris Beckett's The Holy Machine (one of the best, most intelligent sf novels I've really in really quite a long while), Gary Shteyngart's Super Sad True Love Story, Jeff Vandermeer's Finch, Science & Islam: A History, by Ehsan Masood, and Charles Yu's How To Live Safely In A Science Fictional Universe, all 99p.