I'm looking for a good, in-depth resource for load testing REST APIs and web services that goes well beyond "beginner load testing". I'm wanting a technology-agnostic resource that focuses on the goals and techniques, and maybe suggests tools to accomplish those techniques - but not something that is tied to a particular stack or toolset. If the resource includes related testing, like performance and scalability for web apps & web services, that's a bonus.
To be clear: I'm not looking for articles on how to load test, tutorials, or tool recommendations; we're already doing basic load testing and getting value from it. I want something in-depth to help identify holes in our current approach (if any) and improve what we are already doing, plus wanting to round out my own knowledge on the topic. A quick look on Amazon isn't getting me anything that sounds promising, so I thought I'd turn to the experts.
Any recommendations? Is there a clear "best in class" resource for this?