I'm just going to say it: this book was a massive disappointment. I'm an avid Pratchett fan, I've read almost all the Discworld books and loved most of them, but this one was mostly a piece of tripe redeemed by, well, not much. All those Pratchetty ideas are there, sure enough - those themes of how people tell stories about the world, of compassion and of humanism; but that's it. You remember those quirky, distinct, highly-coloured characters of The Truth or even The Carpet People ? Well, they're gone. Pratchett has appropriated a cast of celebrity characters - Charles Dickens, Henry Mayhew, Sweeney Todd - to people his novel of a distinctly Morporkian Victorian London. All well and good, historical reference, yes, very fun for the reader. However, every member of this diverse cast speaks in exactly the same way . Disraeli uses the same vocabulary and syntax as Dodger, the eponymous hero of the novel who works in the sewers. More than this, they speak exactly the same way no matter what circumstances they encounter. For instance, the bit at the end where Dodger is pretending Simplicity is dead - well, he seems to forget this pretence and launches into an eloquent speech about the criminal that did it! I am frankly astonished that his plan worked. I know this is a YA novel, but characterisation is still important, besides which, Pratchett inserts some references to Dickens novels that only an adult could be expected to understand - how many twelve-year-olds have you met that have read Our Mutual Friend ? Pratchett is also writing for an adult audience, obviously, so his novel requires adult characterisation.
Sorry, that was a bit of a rant. There are some good things in the novel, as I said before, but they're weighed down by the dialogue, of which there is a lot.
Oh, and Pratchett specifically says that Dodger is not a historical novel but a "historical fantasy". Er, sorry, but it is a historical novel. There is nothing in there that could possibly mark it out as a fantasy.
I'd like to say that I'm going to stop reading new Pratchett novels, as they are invariably disappointments. Unfortunately, I don't think it's going to happen, because there is always the vain hope of something better from one of my favourite authors.