This time period is vast, it starts after Episode 3 after all, and actually continous past episode 6 - Will the book only cover the exact period in episode 4-6 or actually do the whole era?
I do hope for the latter as that makes this time period the ten times more interesting. Other then that my favorite is the Old Republic.
As mentioned, the Rebellion Era officially and canonically starts directly before the Battle of Yavin and goes until the formation of the New Republic in 4 ABY.
The game, according to the devs at GenCon, actually covers the period of time between the Battle of Yavin and the Battle of Hoth (so about 3 years).