Although this book is middle-grade level a read, it's full of text and suitable for anyone older too. A quick read, this is a story in form of a notebook Rey wrote as a guide for anyone trying the scavenger life on Jakku, with some drawings and pages folding open.
Themes of the guide are: locations, what Rey's home and speeder look like, life forms on Jakku, on the graveyard of ships (with a guide to each ship type and what each can offer), a detailed survival tips guide - including on dangers, what the valuable trades are, what's in Rey's tools satchel - and finally on what's (and who are) at the Niima outpost.
Included also are some 'attached' stuff like details of Rey's AT-AT, "Travel Advisory on Jakku", (Empire) food ration user guide, Happabore medicine guide (one of the working animals there), a look on crashed Imperial Super Star Destroyer, and details map on salvageable on a X-Wing.
You get a sense of Rey's great wisdom on how to survive, and the skills that she'll find useful from TFA on... and a sense of her loneliness while holding stubbornly on to hope that she will be picked out of this life again.
The book ends with the first few scenes of The Force Awakens, so that might be spoilery for some who haven't seen it yet, but it ties into the guide-story nicely. It was written as a way to pass the time, and to cope with the harsh life on Jakku, yet it is very entertaining to read, and not heavy.