No spoilers in this part, just an opinion on the book itself, for whatever it's worth:
After the initial fun of reading where the movie plot is going, I'm starting to see a couple of problems with the book, though.
Thing is, for those who plan to read the book after seeing the movie, it might be, eh, anti-climactic.
Parts of the book are nicely written, and other parts are kind of... well, it lacked a good description of what is really going on in some scenes, and it may very well confuse people on the depiction of certain characters. That is, I'm concerned the inconsistency of the quality of the writing itself will turn some people off who are not familiar with the TMNT's characters and will mis-judge the movie on reading this book. Some people seem to have drawn conclusions based on just that, from what I've seen on some message boards.
Personally, I've heard this sort of talk before, concerning LotR, and when finally seeing the movies, all concerns on my part were banished.
Spoiler, highlight to read:
Uhm... I think Leo is getting the short end of the stick in the initial storybook... he's making himself out to be a bit of a brat. I'm optimistic that this was simply sloppy writing and misleading. And that in the movie, all will be made clear. Otherwise, Leo fans will be chasing Kevin Monroe out of the country... 