I seriously don’t understand why you do not study one of the classical philosophical tracts. It is probably the only one that you will accept as “challenging but not to the point of boredom and interesting but not to the point of pop culture.
No romance, no violence, no foul language, but written on an 11th grade level of interest and not tragic.”
The book of Job.
Chances are that you can even study it in the original language and not have to use the Greek or Latin translation!