This book is unlike any other Heinlein. It's way more surrealist and weird. Also, it's a mystery novel where I really *didn't* see the ending coming!! So many mystery novels have super obvious twists, but not this one. It's genuinely really, really awesome. If it's not already an episode of "The Twilight Zone" it seriously should be.
Another reason I liked it--I've only read two Heinlein novels where he didn't go on and on and on about rape--this one and Glory Road. Granted, the gender of the book is totally 40's Humphry Bogartesque (the words "dame" and "broad" are never used, but they might as well be), but I can get over that. I just fucking *can't* get over Heinlein's obsession with rape--nor do I want to. However, in the rare instances where he doesn't get all rapey, I actually love his books.
So even if you generally hate Heinlein, I suggest trying this one. It's nothing like his other books (and that's a good thing!).