This is not what I would typically pick as a 4-star read, but for my kids, it was a 4-5 star read. It is a calm story--not crazy action-packed. We read a couple of chapters a night before bed and for my anxious 7- and 4-year-old, this was a great read. Nothing scary, but a few things that are a bit suspenseful. Nice story about friendship. Everything works out. The description and language is soothing. We've read all three books in the trilogy now and recommend it for kids who like calmer stories.
I will note, however, that the 2nd and 3rd books in the series have a lot of typos. We were reading it out loud and could correct the typos as we read, so it still made sense to the kids. But if your child is reading this on his/her own, it may be a bit frustrating.
We look forward to reading the companion novel, Haven.