There is a good and thorough book by a music industry lawyer called Don Passman: "All you need to know about the music business."
It is not a quick read, but may stop you getting stiffed by someone more knowledgeable.
There is a lot more to a record deal than 'royalties,' and the other items on the account are not trivial !
He does give typical percentages and amounts that artists of different statures can achieve.
Absolutely, and let's not forget the wonderful 'The Musicians Guide' by Marcus Taylor.