I've done the Mystery/Thriller, the Sci-Fi/Fantasy, the quarterly Cookbook, and the quarterly Military History boxes, and they've all been great. The Sci-Fi/Fantasy boxes especially are solid.
I've had several of their boxes, and every one has been fun. Currently, I have cookbooks and military history, but I'd have to say Strange Worlds is my favorite. Still, none of them disappoint.
I love the different types of books that come from this subscription. They're all guaranteed vintage, and every one I've received has been great.