Here are a couple of eBooks focusing on architecting .NET Core applications on my reading list.  The first one titled "Architecting Modern Web Applications with ASP.NET Core and Microsoft Azure" is written by Steve Smith and focus on monolithic applications.  The second one is titled ".NET Microservices: Architecture for Containerized .NET Applications" written by Cesar de la Torre and focus on microservices and containers-based architecture.  Happy reading!