I think that every night I read Radium Baby, I turned to my wife at least once and said: "This is such a weird book." or something similar to that effect. I really had no idea what to expect going into it, and I think I spent the first dozen pages or so trying to figure out whether or not the book was going to be serious. At that point, I had the revelation that I was reading something like Lucasfilm's game Maniac Mansion. I loved that game. Once I was there, the book was a quick, and fun ride. I haven't read a book like this book. If this is a genre, it's my first taste of it.
I don't know why, but the biggest laugh that I got out of the book came early; it was when Chapman thinks he has been speaking to Herbert Wise, and spins around the empty chair:
Chapman marched over to Wise's chair and yanked it around. It was empty. All this time Chapman had been complaining to an empty chair. "Oh my God!" screamed Chapman.
Maybe I have a weird sense of humor, but for me that was golden.
I think the book's biggest success is that you really never know (or feel like you can know) what is coming, and it propels you forward at an exciting, almost frantic pace. I could empathize with Sam, and I enjoyed his character, as pathetic as he was. I felt connected to him the most when the freaky Bishop was about, and thinking on it, I agree with humanodon that it would have been a nice twist if he joined the hide-and-seek game. The book was just so weird, it would have made perfect sense to me. I also liked Gloria. After her early solution to the Gettysburg puzzle, I became invested in what she was up to.
While I read the book, the thought came to my mind that I almost wish I hadn't seen the cover before reading. I think that knowing that there would be huge hornets and a killer robot may have detracted from their weirdness and a sense of surprise. I don't have many negative things to say about the book, except that the large number of adult characters was at times confusing. I'm not sure how it might be done, but I feel like one or two of those characters could be combined into a more multi-faceted character that has more time spent upon him.
Although wacky (and at times it was too wacky for my tastes), Radium Baby has a sinister nature to it, which I appreciated. The adults don't give a damn about the kids, and that is just a bit more than they care about themselves. Almost all of the adults are dysfunctional. The Bishop is scary as fuck, and I do have to say that the Pepperpot mansion was written effectively. It felt extremely wicked. StJohn, I think you might have a talent here. In fact, if that sinister nature of Radium Baby were turned up a notch or two, IMO it would stick with me all the more.
Those are my initial thoughts.