A follow-up from one of the original episodes, in which Spock gets an adult son who is brought forward in time from the alien ice age past of his conception. It was an enjoyable, easy read, and Zar was a sympathetic character. I particularly liked his relationship with McCoy, who he seemed to bond with a whole lot easier than Spock. The relationship between father and son was strained at best, but there wasn't a whole lot of tension because I was expecting the reset button, which arrived on schedule and to obvious effect. However, given that so much of the early story focused on Spock, it was a little strange how he almost moved into the background as the story progressed - Zar was very much the main character for most of the book, with the Enterprise crew as much supporting cast as anything. On the one hand this has made for an interesting character study, but on the other I wonder if a more sustained focus on Spock might have made the story more compelling. Still, I understand there's a sequel, so I'm curious to know how that works out.