Separated into four parts - The Secret Diary of Adrian Mole Aged 13 3/4, The Growing Pains of Adrian Mole, The True Confessions of Adrian Mole and Adrian Mole and the Small Amphibians - the quality and tone sort of leaps wildly when you hit the halfway point and finish Growing Pains.
I really enjoyed the first two books, which - given the abrupt ending of Secret Diary, and immediate succession of Growing Pains - really feels as if they should be just one book anyway, as they cover the teenage years of Mole as he declares himself an intellectual, churns out abysmal but fascinating poetry, waxes on about the Norwegian Leather Industry, and lusts after Pandora. It's also interesting as a look at the '80s, as I didn't realise at first that they were written in the '80s as opposed to looking back at them. The various quirks of the diary format - the daily updates, some of them tiny and some of them epic, some of them written retroactively to account for terrifying motorway excursions, the snippets of poetry and letters - work entirely in the first two books' favour.
Unfortunately something goes terribly wrong after Growing Pains. A year and a half is inexplicably 'lost' before the next update, and the time line also seems to have gone wandering - a year and a half has passed according to the dates, but only six months according to the diary itself. Continuity errors crop up. Characters who had stepped out of the series are back where they were, little details are forgotten. The tone is rather different, too. The diary format is sustained in parts, but goes all over the place, with updates no longer taking place every day but every other month. There is a much greater emphasis on letters and diatribes, some purporting to be read out on BBC Radio Four. The whole thing feels like it might not be canonical, like Adrian is merely fantasising about these fantastic events (something that would be quite in keeping with his character), but when the short work Small Amphibians picks up things carry on in the same vein, skipping ahead and becoming increasingly off the wall. Much of what occurs during Mole's teenage years is either realistic or realistically unrealistic, seen through his oblivious eyes, yet what occurs later becomes increasingly hard to swallow, as if he's either more and more unhinged or the writing is getting looser and looser.
I'm told that the next book, The Wilderness Years, is perhaps the best in the series. I hope so. Certainly the first two books are fantastic. True Confessions and Amphibians are perhaps less worth reading, but assuming they fit into the larger arc of the series, still necessary.