gRPC for WCF Developers
The lead developer of Visual ReCode, Mark Rendle, has written a book in collaboration with Microsoft which is available on their .NET Application Architecture docs site. It explains how gRPC works and how it compares to WCF, with more detailed information on Protobuf and gRPC, all helpfully explained in the context of WCF.
Read gRPC for WCF Developers on docs.microsoft.com
Introduction to gRPC on .NET Core
The official documentation for the Microsoft-contributed .NET Core implementation of gRPC.
Read Introduction to gRPC on .NET Core on docs.microsoft.com
gRPC C# Quick Start
A quick start guide on the official gRPC web site.
Read gRPC C# Quick Start on grpc.io
Protobuf Language Guide
The official guide to the Protobuf Interface Definition Language (IDL) which is used to declare services and contracts in gRPC applications.