Have you come across this?
DS1 picked it up in Ottakars a year or so ago, and read about 50 pages before I could drag him away, with the bribery that we'd buy a copy! Having seen the presentation - different fonts, ink blots, and child-like illustrations - I mentally consigned it to the same category as Horrid Henry and Captain Underpants, and dismissed it from my thoughts.
[OK I admit it I'm an intellectual snob] but yesterday in The Times there was a whole page review of the sequel. I was so surprised by the tone that I picked up the book to have a flick through ... and it's great! Certainly far superior to HH and CU. Ds2 is now reading it, and he is gripped - which is unusual for him.