Also, Gideon the Ninth is $2.99, as is The Three-Body Problem, and Binti is just 99 cents. All three discounts will last through July 28.

Edit: And if you like Gideon the Ninth, you can download act one of the sequel for free. AFAIK, that's a permanent freebie, though this preview may become unavailable for "purchase" once the sequel hits store shelves on August 4.