Didn't think much of "Dad is Fat" - I expected more laughs. The book is basically short-story diary entries, all of which are light-hearted, but none of which are really funny. A few turns of phrase were nice, but nothing you'd really want to remember and tell your friends and family.
A decent book for short reading periods (each chapter is only a few minutes), so it can be read easily on transit etc.
Overall, not a great read.