I think the cricitism here is far too harsh. Yes, it's a shame about the continuity errors, but this IS a work of fiction. What is evident is that Sue Townsend's social/political satire remains spot-on. There are many laugh-out-loud moments. It's not a masterpiece ('Adrian Mole and the Weapons Of Mass Destruction' may well be, however), but it's a worthy addition to the Mole story. As for repeated plotlines, surely that's part of the point: Mole's life seems doomed to repeat itself (i.e. often ending up caring for elderly people, often falling for inappropriate women, taking on bizarre short-lived jobs, and so on). This is where much of the comedy comes from.
My only real criticism is Sue Townsend's annoying trick of inserting herself into the story. This looks like she's trying to be 'clever' for its own sake but it really falls flat. It's pointless and only undermines the brilliant creation that is Adrian Mole. Otherwise, this book is well worth a few happy hours of your life. If you have enjoyed the previous volumes you will like this one, too.