These encounters were said to be inspired by, and useful for the Storm King's Thunder adventure. Most of the encounters are written for levels lower than any character would be once they are exploring the savage frontier in that adventure. Thematically as well, the encounters don't fit with SKT. There were some errors in the text as well. I found it disappointing.
I think as low-level encounters go, this collection could certainly inspire some fun, but as a supplement for use with Storm King's Thunder it doesn't really work.