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.
This pre-Phantom Menace series tells the story of the Yinchorri crisis (referenced in Darth Plagueis). The Yinchorri are violently expanding their empire by invading several other planets. Mace Windu and many other prominent Jedi must investigate and preserve peace. But readers soon learn that Darth Sidious had orchestrated the crisis for his own nefarious purposes. . .
Even in the days before the shadow of the Phantom Menace falls upon the Republic, the rule of the Senate is no guarantee of peace. When conflicts arise, it is the duty of the Jedi Knights, under the guidance of the Jedi Council, to protect the innocent and restore order. When the warlike Yinchorri threaten the stability of the Republic, a Jedi task force led by Mace Windu and including Qui-Gon Jinn and Obi-Wan Kenobi is sent to the Yinchorri system to settle matters, and they soon find themselves facing overwhelming odds on three different worlds.