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.
"Three movies and countless spin-off activities later, these comic books echo the spirit of Artoo-Detoo and See-Threepio to the letter. Some of the pages are as convincing in character to me, as though I were actually there, playing the part. When a character you have created and loved has been reproduced commercially in every way from bubble bath to bubble gum, you can get a little protective. But with these stories, I know Threepio is safe." ―Anthony Daniels