Overall, this is a beginner-friendly book on GraphQL. It starts with the basics of GraphQL query syntax, then moves on to explaining schemas. The book uses the express-graphql library as the backend implementation to demonstrate how to write resolvers. In the later chapters, it covers how to send client requests using both basic "fetch" and the Apollo client. Aside from the fundamental concepts, it also addresses the "N + 1 queries problem", which is a nice addition.
The book essentially covers everything needed for getting started with GraphQL and gaining a general understanding of its concepts. The "in action" sections are explained in great detail, which might feel a bit slow-paced and repetitive to experienced developers, but it is quite suitable for beginners who need a thorough introduction.
In my opinion, this book is a great choice for absolute beginners who have no prior concept of GraphQL. However, for those who already have some experience with GraphQL or have done a basic "Get Started Implementation", it might not be very beneficial. Instead, diving into the Apollo documentation might offer more practical insights and be a better use of time.