Ask HN: How useful is "Patterns of Enterprise Application Architecture" today?

I found it to be very useful. Even though it is a few years old, the underlying concepts of each pattern remain the same and I find it much easier to maintain code when I know which pattern was implemented.

As for newer content, I would point you again to Martin Fowler and his piece on Microservices[0].

http://martinfowler.com/articles/microservices.html

Architecture of Open Source Applications.

http://aosabook.org/en/index.html