Short answers, pulled from the story.
The series was primarily written by Jude Watson. The first book, The Rising Force, published in 1999, was written by Dave Wolverton. Watson authored all remaining volumes, including the two special editions.
Star Wars: Jedi Apprentice was published between 1999 and 2002. The series comprises eighteen main novels and two special editions, concluding with The Threat Within in 2002.
The series is primarily targeted at children aged 9 through 12. Its serial plot development and writing style also attracted older readers beyond that intended age range.
The series follows Obi-Wan Kenobi and his Jedi Master Qui-Gon Jinn on missions across the galaxy before the events of Star Wars: Episode I. The story begins when Obi-Wan nearly fails to become a Jedi apprentice and spans his development from age thirteen to seventeen.
Xanatos is Qui-Gon Jinn's former apprentice and the main antagonist in the early books. He leads the Offworld Corporation and repeatedly clashes with Qui-Gon and Obi-Wan before ultimately committing suicide on his home planet of Telos when cornered by the two Jedi.
Tahl is a Jedi Knight and close companion of Qui-Gon Jinn. She dies at Qui-Gon's side during the New Apsolon storyline after being captured by extremists on that planet. Her death triggers a grief-driven rage in Qui-Gon that requires intervention from Mace Windu and Obi-Wan to contain.