Doss, Mead /ISBN 0396072216 (1976)
This is one of those books they'll have to pry out of my cold, dead hands.
I have referred to this volume so often I'm surprised it's still holding together.
My copy is from 1976 and I'm sure you can get updated versions, but get what you can.
There are a lot of books out there on Musical theatre (some very good and some just
glorified paste-up jobs) but this is the gold standard reference book of its kind.