I have most of the major online books. I am going to say if you want to do this seriously you need 3 books.
1. Bookmaker/The Greek
2. Matchbook
3. BetJamaica
You need The Greek, Bookmaker, or Pinnacle (hard to get money on if you live in the US) for the overnight lines. You use Matchbook because you often find the best value juice wise over there. Then go with BetJamaica because they are fast and they will keep thier lines still for longer then most other books. So if The Greek moves out of your favor you can most likely turn to BetJamaica and get the good line there.