Is there any documentation on the macOS Sierra new logging system? I've been trying to diagnose a problem with a MacBook that won't NetBoot off my Mac Mini server running MacOS X Server 5.2 and macOS Sierra. However it proved to be rather difficult when I came to actually looking at the server log files as aside from the server log they were totally empty, and the server log seemed to be lacking anything useful at all.

After some digging around on the Apple site I came across this post which suggests that Apple have changed the logging system on macOS Sierra, and certainly following the instructions there I can find the logs, but they're still not viewable through the server app, and the official Apple server documentation still talks about logs going into the traditional log files.

Is there any more detail or documentation anywhere on the new logging system, or how to get it to play nicely with the server application?
Most of the logging that was being redirected into custom log files has defaulted back to the system log. As was mentioned in the post you referenced, the log command (man log) is the best way to access the information. 

For netboot issues, looking at log messages from bootpd &amp; tftp should give you useful info.

log stream --predicate  '(process == "bootpd") || (process == "tftp")' -info