The extra bits also include an explanation of Carol Marcus' accent, why McCoy didn't just draw blood from one of the other augments, a completely different "super ice cube" solution for the super volcano, extra info on how their torpedo switcheroo actually worked, and a wildly different take (in my opinion) of the private scene between A. Marcus and Kirk in the first half of the movie.
What we didn't get in the book was any new information on the aliens or new crew members*. I think a crew member is identified as Bradley and some of the Captains and ships are IDed in the emergency meeting at Starfleet HQ, but that's about it. Also still no reason given why Carol Marcus needed to change her clothes in a shuttle craft while speaking with Kirk.
I think Foster did a much better job with this novelization than the previous film's. It felt much more substantial and polished.
*Keenser is identified as a Roylan, but I couldn't remember if this information was given in the previous novelization or revealed here. Also unsure if it matches the name given in his origin story in the comic series either.