Gary's book is relatively groundbreaking because it exposes a lot of myths. But it's a bit heavy to read.
I just read "Six Weeks To OMG". It's similar in some ways, but MUCH easier to read and funny too. It does have a lot of shocking ideas in it (until you realise doing the opposite is the really shocking thing).
The main thing is that I've lost a stone (14 pounds) in just under 6 weeks and feel light!
Six Weeks To OMG