Surprisingly good & comprehensive. Guides you step by step through (almost) all the building steps for near-production-quality services. It's very detailed & still - it doesn't make shortcuts. There are still few minor topics that could have been covered (like versioning, discovery services, deployment practices, etc.), but these are details one can forgive :)
Ok, some more remarks:
1. monitoring is covered, but only very simple black-box monitoring
2. this is NOT really a book about .NET Core -> it's used as a platform for building microservices, but its specifics or advantages are never really mentioned, it's just there, no excitement (same applies to NancyFX)
3. as a side effect this book is quite a nice, _practical_ guide to OWIN - the word "practical" is important here: author shows how to use OWIN's extensibility for one's advantage. Nice.
4. entry threshold is minimal (well, you have to know C# ...)
In few short words: very decent book. Especially if you're already well familiar in .NET & you did similar architecture with a slightly different tech stack. It's really interesting to observe how some topics are being approached (& well described by someone else). Recommended.