Got around to watching this one, and it's not great.
FX wise it's all over the place, with a few cool things and a lot of meh, some outright bad.
Some of the smaller changes are just baffling in a "why did they bother changing that?" way. The family apparently lives in Los Angeles in this version?
They reference but don't show some of the better parts of the book (Aunt Beast) - but that makes sense for time constraints.
Overall though I'd say it's pretty true to the book, it's just rather sloppily made - feels like the director had a big budget but not much experience.
The ending in particular is very rushed. Characters are evil out of no where, with the flip of a switch and everything is resolved in the same way.
It really would have been hard to get this one right as a movie, and they didn't. Not the worst movie, just not worth your time.