Although not a good read (in terms of being engaging or interesting), you'll find that a lot of security professionals will use something like the Center for Internet Security (CIS) benchmark when doing a formal audit or configuration review of RHEL (or any major Linux distribution for that matter). They will run a command line tool that will check the system's config against every item in the benchmark. The tool will generate a report with pass/fail outcomes for each item plus hardening advice. It's not perfect but it can be a decent starting point before you do further manual analysis of your system.

More info about the CIS benchmarks: https://benchmarks.cisecurity.org/downloads/benchmarks/

The RHEL 7 benchmark: https://benchmarks.cisecurity.org/tools2/linux/CIS_Red_Hat_E...

The DISA STIG was my starting point when deploying RHEL6 boxes. I don't believe the STIG for v7 is available yet, but I haven't checked in quite a while.

The CIS Benchmark is also quite extensive, and there is a lot of overlap between the two.