Graham Chapman is the most mysterious of the Monty Python team, what with him being dead and therefore unavailable for documentaries, interviews and Monty Python tribute nights on Channel 4. However this book redressed the balance- a very thorough collection of Chapman's sketches, speeches, serious essays, letters, and select extracts from his book "Liar's Autobiography", many of which you haven't seen before.
It really shows Chapman's breadth and depth. He was so intelligent, both broadly as a doctor and an observer of the human race and on specific issues such as homosexual rights, and with a scathing wit.
My sole criticism of the book would be that it is arranged by group- all the letters in a group, then all the sketches, and so on. When I re-read this book, as I will, I'll probably read it in a random order to get the full contrast between comedy and tragedy.