Betcoin has two books, Betcoin and Gamebetr.
This is the first time I hear about Gamebetr. Don't you mean Playbetr? Playbetr used to have their own site but merged with Betcoin some time ago. I remember it from my withdrawal fees thread. Betcoin uses the betcoin.ag domain, while Playbetr got redirected to new.betcoin.ag. Even if you try to access playbetr.com noew, it will redirect you to the new Betcoin domain.
Playbetr was the sister book of Betcoin that has closed. They sponsored Paris Saint-Germain for 3 years. Gamebetr is the legacy version of Betcoin. It's simple to use and generic. Betcoin is now the modern version with different lines and limits.