Dodger's Guide to London comes as a companion to the novel Dodger and provides us with a casual look at what life was like for the lower classes of Victorian London.
It's a good place to start if you're looking to start researching Victorian London, as it has some very good references and recommendations for further reading. Paul Kidby provides the wonderful illustrations that always accompanies Terry Pratchett's work, as well as some real-life photographs that do not disappoint in bringing the era close to hand.
It does not contain much humour, though I would suggest this was a child-orientated book, and as such it can get a little boring. In-and-out reading would be best, and definitely it is a referenceesque book as opposed to any other kind. Be wary of the fictional elements that Pratchett provides, as these are not factual and may trip you up. Altogether an interesting read.