Check. This. Out.
Now, it's not unusual to find a book that parallels your idea. You get a cool idea, then find out that someone did a similar book in 1974. This one is crazy, it comes out summer 2010! Yeah, brand new book--almost the exact title--and with a train on the front! What are the odds, I've never seen this book before, was just playing with the word "hibernation" this afternoon, feeling pretty clever. Wow, just goes to show you, there are no new ideas under the sun.
Anyway, best of luck to Michelle and Kurt, this looks like an adorable book. Now I need to think up a fresh idea. Quick.