Most recent purchase was Apocalypse Keys, but since then I asked for Rotted Capes for Christmas, so I've been reading that right now! I bought Apocalypse Keys because I really like the premise of monsters ending the apocalypse (and I like Hellboy), and I bought Rotted Capes because a friend of mine is really big into both superheroes and zombies, and I want to run a RC game for him.
I've run Apocalypse Keys and really enjoyed it, the mystery set up is well laid out and the mystery clock makes it easy to pace. I'm a little less certain of Rotted Capes, but I haven't yet made a character for it and character creation is usually where I iron out a lot of details.