My book (my first and only) <https://www.packtpub.com/application-development/d-cookbook> got $3000 advance, plus an on-time completion bonus, and now, two years later, continues to pay me ~$200 royalty checks in excess of the advance every quarter...

That's not a large sum of money, considering that it took about 6 months of nights and weekends it took to write the book, but it isn't nothing either.