As a novelization based off of the screenplay, this book doesn't quite have the impact of the movie, but it gives some interesting insights into the characters and their motivations. I really really liked being able to get inside Kylo Ren's head... He is honestly my favorite character, not because I necessarily like him, but because I find him fascinating, and this novelization added so much more depth. There are a new changes that were obviously made for filming, mostly things that were cut for time so it's nice to have this to expand somewhat on the scenes. There are also a few points made here that explain questions brought up during the movie in regards to how someone was able to do something, or what happened next to specific characters... I can't get into details without spoilers, though.
This is one of the rare cases where I like the movie more than the book (I loved the movie!) but this is a good supplemental resource.