This free, complete, O’Reilly ebook shows how service meshes work & provides a path to help you build or convert applications. It explains how a service mesh provides a configurable infrastructure layer that makes service-to-service communication flexible, reliable, and fast.
This short and free pamphlet is currently the best introduction and overview of service meshes available. As the technology is so new resources (especially those at a high level) are exceedingly scarce. I personally believe service meshes such as istio will soon revolutionize networking just as devops practices have drastically transformed our view of infrastructure. This small text is where to start.