These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Mass Effect: Deception
Base Breaker: While the novel itself is near-universally despised, fan opinion is divided over the revision (which still hasn't materialized). Some fans are optimistic about the revision and hold BioWare to its word, others point out that the novel's problems run far, far deeper than the continuity errors and that just fixing the lore errors isn't good enough to redeem Deception (specifically saying you'd need a total start from a blank canvas with a new writer), and then there are those who feel that the promise of the revised edition was just damage control and it will never actually happen.
Canon Defilement: There is a list of its many, manycontinuity errors as linked below. Let's just say it'd be easier to make a list of what it got right. Good thing later editions will fix these problems.
Idiot Ball: Aria uses next to none of the security she used in previous books/the second game. Luckily for her, Kai Leng has forgotten about the advanced tactics he used in previous novels as well.
So Bad, It's Good: Many of the more infamous Kai Leng moments are also this. Leng eating Anderson's cereal was actually highlighted on the forums as a moment to be kept in the revised edition because it's so utterly hilarious. And frankly, Leng is so petty (see: him sending Shepard insulting e-mails in 3) that he'd probably do that.
Even after their apology, BioWare still get accused of this for approving the novel in the state it was in. Especially since the writer claims two BioWare officials did look it over.
Unfortunate Implications: This book has offended both gay people and autistic people. The former are offended by the book having a case of a gay character being retconned into being straight (something that needs to be delicately handled, if not outright avoided). It's offended the latter group by saying that you can grow out of being autistic, something for which there is no scientific basis. It also implies that autism is something of a childish phase.
What an Idiot: Late in the novel, Hendel threatens biotic harm on Aria in the middle of her private room in Afterlife. He's damned lucky all she did was tase him.