Monk's biography is fantastic. But I have to disagree, it gives an intimate picture his life, relationships and general outlook, but only glancing snippets of his philosophy. If you are interested in his thought, you would do far better just reading Wittgenstein himself, or reading one of the many fantastic overviews of his work - I would recommend Hans Sluga's book, the Routledge introduction to the Philosophical Investigations, and the Cambridge Companion to Wittgenstein.
I think we're probably talking about different audiences. If you're an undergrad studying a philosophy minor then sure, go to the source. But if you've read a couple of Virginia Woolf novels and are interested in the Bloomsbury set, it gives you enough of a flavour. I studied both early and late Wittengstein at university and I certainly wouldn't recommend the Tractatus to anyone except as a novelty, and although the Philsophical Investigations are more approachable, they quickly become tiring for someone not motivated to invest some time in reading them slowly and thoroughly. (I know this from the time when I was reading the Investigations and badgered other people to read them because I thought they were so fantastic!)
