Whatever the directives from CBS or what happens behind the scenes, the reader still has to deal with what's on the page as presented. First of all, I think it's well-written and the first few chapters are pretty good. However, I agree with the crit that it reads as a bit disjointed because of the way it is spilt into two sections.
Moreover, the author is never going to win when he puts in lots of established characters, half of the readers will love it, the other half will not - I'm in the half that didn't - it also read to me as fan wank, like the Star Trek universe should be full of people playing the banjo and marrying their cousins. Hitting over us the head with "see see this is how the last Star Trek timeline came about, see see" wasn't very good either - I'm avoiding DTI for that very reason as I expect more of the same, much more.
Still at least it's got the rare merit of being one of the few recent TNG-era books that doesn't present unpleasant or degraded versions of the characters we used to watch on the telly.