For the most part, the book seems to hold up as published. I don't agree with a couple of things, like the dating for TWoK vs. Space Seed. But there is more that is correct than not in the book, IMO.
A far more troubling question opens up from the Okudas' insistence on including a period of time for the conjectural 'Phase II' adventures following TMP. Sure, it's clear that a lot of things were changed between TMP and TWOK, and the Okudas wanted to reflect that it appears to have been quite a substantial amount of time between those movies in-universe. But it's this that opens up the biggest can of worms, because in terms of a realistic time-frame in regards to time since the events of "Space Seed", TWOK can't be too
far from TMP. Virtually the entire TOS movie series is kind of bumped along in time to take into account Kirk's (conjectural) second five year mission in the refit Enterprise, and that's what causes most of the headaches until TNG restabilizes things again with it's firm setting.