The Crystal Star/YMMV

Non Sequitur Scene: Pretty much the whole book. Han does refer to Hethrir in Millennium Falcon, though, as does Leia in The New Rebellion. The kids' kidnapping also gets mentioned once in a while.
Ensemble Darkhorse: Lusa for some fans, being brought back for the Young Jedi Knights series and then unceremoniously and unspectacularly killed - offscreen! - in the New Jedi Order series.
Fanon Discontinuity: Fans would much rather deny this work exists.
In Name Only: A major criticism of this book is that it's not really very Star Warsy at all; if anything, the plot is more akin to a Star Trek story. (Which is unsurprising, given that Vonda McIntyre had written a few Star Trek novels in the past.)
Memetic Mutation: While the book isn't well-liked by Star Wars fans, the creature Waru was considered so bizarre that he reached a memetic status rivalled only by Master K'Kruhk's "Freakin' Sweet Hat" and the badassery that is Kyle Katarn.
They Wasted a Perfectly Good Plot: Fandom never really forgave the book for leaving potentially fascinating Eldritch Abomination Waru a giant Non Sequitur Scene while focusing too much on Card-Carrying Villain Hethrir.