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.
In this fourth volume of the Jedi Quest series, Anakin Skywalker and Obi-Wan Kenobi face a very elusive adversary, one who is as cunning as he is evil. After all, how do you defeat an enemy whose riches buy unlimited power, who is a master of disguise, and whom you cannot find? Their foe will stop at nothing to undermine the Republic and draw others to the dark side. And if the Jedi do not stop him, the whole galaxy will be in danger.