Puritan John Owen wrote The Mortification of Sin⁂ to address the "obvious difficulty that most professing Christians have in dealing with the temptations that surround them" (page vii), and this abridged version was published to make it "more accessible" to contemporary Christians.

Based primarily on Romans 8:13 ("For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live."), Owen fleshes out his thesis:

The choicest believers, who are assuredly freed from the condemning power of sin, should also make it their business all of their days to mortify the indwelling power of sin (page 2).

This work points to the gospel and the Spirit rather than legalistic efforts without diminishing the duty of the believer to actively fight sin.

Having not read the original, I can’t compare the two, but I found this version fairly readable. I would recommend keeping a dictionary nearby, preferably one like the OED with historic definitions, because I occasionally encountered a word or use of a word that is no longer common.

This is a book that I can see myself reading again frequently, and I would like to read the unabridged version at some point. I highly recommend it.