The Humble Bundle, which ordinarily sells collections of independently produced video games, is currently selling six sci-fi e-books. You get to set the price, but if you pay more than the average (which is right now floating around $11) you get two extra books—Old Man's War by John Scalzi and Signal to Noise by Neil Gaiman and Dave McKean—thrown in, too. (And! You get to determine how much of your payment goes to charity.) The books are DRM-free, which means you can load them onto any e-book reader in the world, and unlike most e-bookstores, you get to own the file forever, too.
I haven't read most of these books, but I can tell you that Kelly Link's two books of short stories, Magic for Beginners and Stranger Things Happen, are totally worth the $11 on their own. She's one of the best fantasy writers in the business today. In addition to those two, you get Cory Doctorow's newest novel, Pirate Cinema*, the first book in a "modern military superhero saga" that "chronicles the battle between Earth's superheroes and a transdimensional Third Reich," and a highly promising novel set in an alternate-universe Johannesburg that stars a journalist with a sloth on her back. I don't think you can go wrong with this deal.