I agree completely, it was a great read. Monk's writing was absorbing. I was wrapped up in the unfolding of an interesting life. I loved this biography.
I read it after reading House of Wittgenstein whose focus is on the whole family, which provided me with a deeper family context for a better understanding of L.W. (as well as just being a good story). Its not necessary reading except for those who are really into L.W. though.
I also recommend the the "How to Read Wittgenstein" book you mentioned - it is well worth the time and money (both modest). I feel like it provided some intellectual context to his works that enabled me to better appreciate them.