If you have not figured it out yet, the bulk of my references this year have been from C.S. Lewis. This is because my 2017 goal has been to read all of his published works. Hitting about the halfway mark, I (re)read Mere Christianity last week.
I strongly believe that The Great Sin (chapter 8), apart from Scripture, maybe one of the most important things to persistently reread.
C.S. Lewis originally delivered this as a radio lecture, so for my own edification I recorded myself reading this chapter so I could listen to it while driving or running this summer. (Its a rough recording but if you want to listen to the chapter, here you go.)
Also, here is the pdf if you’d prefer to read it for yourself: The Great Sin.