I don't think I've read anything by Zahn yet.
I've enjoyed basically everything I have read, except for Labyrinth of Evil, which seemed somewhat dry. Possibly because I'd bought it expecting to see more of Grievous... when he seemed to spend most of the novel sulking, and most of the action was centered around Obi-Wan and Anakin. Ugh, Anakin... is it sad that I just generally like him more as Darth Vader?