I was disappointed. I didn't buy the science, I didn't like the all questions, all the time prose style, I didn't like the way the time jumps killed the story's momentum, and I wanted the quirky, free-spirited hippie guy to get hit by a truck.
But my real problem is that the book is about the wrong Saavik.
There are two ways of interpreting Robin Curtis's Saavik in Star Trek III. Some people think she's a convincing and interestingly drawn character. As for me, well, I think she's a combination of weak writing, weak directing, and weak acting, and nowhere near as interesting as the Saavik of Star Trek II. MWB really has captured Curtis's Saavik, and to me, as someone who was really impressed by Saavik in 1982 and who doesn't get what she's been so underused in nearly thirty years of Trek novels, that's a hell of a lost opportunity.
I liked MWB's previous books to varying extents, from "that was okay" to "that was really good" to "that was damn near brilliant, but for this one flaw." This one just didn't work at all for me. Glad to see it made some people happy, even if I'm not one of them.