Reading the novel *spoilers*
Just picked it up. Only about 20 pages in. So far, it’s all extra stuff. Not even to where the movie begins.
The neatest part so far is Luke has a dream where he never left Tatooine and “got involved”. It’s a neat little sequence.
EDIT 1: There is a whole theme focusing on Finn's determination to protect Rey. Rose is frustrated by this and even a little jealous. I wish this had been kept in the movie. This is cut dialogue mostly, not cut scenes.
EDIT 2: One interesting note: In the TFA novelization, there is an extra scene where Rey and Poe meet. This was contradicted when TLJ came out, as the movie shows Rey and Poe first meet on the Falcon after the battle on Crait. The TLJ novelization, however, omits this part, making the novelizations consistent with each other.