BBY/ABY is used to position items along the Star Wars Timeline. BBY refers to Before the Battle of Yavin. ABY refers to After the Battle of Yavin. The Battle of Yavin in Episode IV: A New Hope occured in 0 BBY/ABY.
The Youtini Expanded Universe Ranking system is a 1-5 scale that ranks EU book quality, difficulty, and importance. Books closer to Level 1 are easier to read and understand, more important, and of higher quality.
On the run since the destruction of the Starkiller Base, General Leia and the remaining handful of Resistance have barely managed to survive, much less strike back against the superior forces of the First Order. Running low on options, Leia decides to reach out to her former allies, the Mon Calamari, whose shipyards once powered the Rebel Alliance.