The Columbus crew exploring Mu Arigulon was by far the most interesting storyline. I loved everything to do with the Community of the Children of Farrezz.

The crew of the Hofstadter got caught in bad weather early on (why was that a perspective we needed?), and McCoy still on the Enterprise was too wrapped up in the guilt of being a dead-beat dad to be of any interest (what was the point of the flashbacks?).

I hate that Emelra'ehn died
adventurous challenging emotional mysterious tense fast-paced
Plot or Character Driven: A mix
Strong character development: Yes
Loveable characters: Yes
Diverse cast of characters: Complicated
Flaws of characters a main focus: Yes

A wonderful novel that added depth to Doctor McCoy's history and what made him the man he was when he became CMO on the Enterprise.  A well thought out story, that played to the strengths of the characters.  Enjoyed the first person perspective of McCoy, and seeing his inner struggles/demons come to play as he had to deal with the results of the spatial distortion.  A highly recommended read for anyone who is a fan of Dr. McCoy.  
(The secondary plot with Kirk & the away team wasn't as well thought out and should have been left out.)