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.
Star Wars: Book One is a hardcover collection of the first three volumes of the Jedi Prince young-readers series from authors Paul and Hollace Davids: The Glove of Darth Vader, The Lost City of the Jedi, and Zorba the Hutt's Revenge.