I bought this book just recently without quite realizing that AOA hasn't received any updates since 2012, and that the ADK, even, has been retired. I'm getting the impression that Arduino + USB Host technology is dead or dying. Is that accurate, or have I managed to misinform myself?

I'm really interested in learning about Arduino and hardware generally, and as a professional Android developer, this seemed like the perfect way to do it. Any pointers from others on this forum would be greatly appreciated. Thanks.