CommonsWare is here to help you through the challenges of Android app development, whether you are new to the platform or are deep into a project!
The Busy Coder's Guide to Android Development offers over 200 chapters of Android knowledge, from the very basics through highly advanced topics. Updated several times a year, it covers Android Studio 3.1 and the latest Android SDKs, including Android 8.1 and the P Developer Preview.
Not only does subscribing (only $20!) give you that book plus six months' worth of updates, but you also get three additional books and six months' work of their updates:
Android's Architecture Components, for a deep dive into this important set of Android libraries, and Android app architecture in general
Exploring Android, a series of hands-on tutorials for creating an Android app from scratch
GraphQL for Android, for accessing GraphQL-powered Web services from your Android app