What to read?
 

I'm confused by the different motor nomenclature and how it translates to performance. For example, I've had a Hacker C50 recomended for a Goldberg Cub project, but the C50 comes in many versions - 9 -11 -14 etc. The Hacker tables give representative plane types, prop diameters, etc, but where do I go to learn the WHY of the different examples? I'd like to be able to make an intelligent choice without having to post plantive requests (like this) every time something new comes up. Surely someone's published a book?