This is a perfectly competent overview of JAX-RS but it is a little verbose and can be repetitive like API reference documentation. Annoyingly, its code examples are always followed by text explaining what the code did, even when that is blindingly obvious. I always prefer code with inline comments.
Similarly, you can learn most of this just by exploring a well-commented example project, because JAX-RS is a rather straightforward framework. I think the ideal JAX-RS documentation would just be a walk through of such a project, with some extra text to explain where the code might have done things differently. It would then be a smaller book, but I'd love to see that as part of a bigger book that explored the wider issues involved in designing, implementing, and monitoring fully scalable systems.