3 stars is generous. This is a blog post made into a book.
I read it because I've trekked in Langtang, Gosainkund, and Helambu myself, so it was fun to read about places I've visited and can visualize. (in fact, I was in Langtang for the 2015 earthquake).
I've even stayed in at least one of the same tea houses.
The book is a bit too detailed about the monotonous aspects of trekking, and lacks anything out of the ordinary or insightful.
I recommend it to anyone planning to visit the area for an idea of what it will be like. At the end there are helpful sections that break down cost, etc.