Thanks for the comments hedrick! I've never read the book so I don't have anything to say one way or another about it. I've seen it
recommended elsewhere in an updated form and was curious what others thought about it.
But I think I smell what you're stepping in though about obsessing over sin, which is actually why I was curious about what Presbyterians/Reformed Christians might think about it. Coming from my old tradition, the idea of a manual on "overcoming sin" in a monergistic tradition struck me as bizarre to begin with. Not of course that your tradition endorses antinomianism (and I'm not endorsing it either), but it does seem strange. Maybe I'm missing Owen's real point though and I'm sure I'd have to read him to get it if so.
I agree that it's kind of interesting. There are two theological issues involved in sin: (1) justification by faith; whether you're Reformed or not, all Protestants would say that you salvation is determined by whether you follow Christ, not specific sins (2) predestination; lots of people think that means that it doesn't matter what you do. So I can see why people might believe that Reformed folk might not battle sin.
However, historically the Puritans (the main Reformed tradition from which US Presbyterianism came) were just as concerned about sin as any other Christian tradition, and more than some. Owen is from that background.
Second, I'm not sure how much predestination matters on a day to day basis. Sure, God's plan says whether you've saved or not. But you don't know whether you're elect. God's plan works out through "secondary causes." That is, when God wants to save someone, he makes sure that they hear the Gospel and respond to it. Their response involves their will, even though the will is moved by God.
Note that Owen warns people that sin tends to lead us away from God. People don't tend to fall away at once. Rather, it tends to happen slowly, moving further and further away. It's not that there's one big unforgiveable sin, but that sin tends to desensitize us to God's voice, and over time we can end up losing faith. And if you don't have faith, you're not justified. Now if you look at things from God's point of view, when this happens it's someone who wasn't ever part of the elect, and that fact is working itself out in history. But we can't see God's plan, at least not in this life. And if God is moving us to be concerned about our relationship with him, part of our response is going to be a concern to keep our relationship in good shape by following his will.
But there's one other aspect. Christianity isn't just about saving our butts. Christ is our redeemer. And redemption means not just papering over sin, but actually dealing with it. The Reformed ordo salutis says that Christ dies for us, God unites us to Christ, we receive that in faith, and that produces two results: justification, which is our status as proper followers of Christ, and sanctification, which is our process of living and developing as Christians, including repentance and growing in Christ. I have argued elsewhere that while our justification our status as God's people doesn't depend upon our success at having defeated sin, defeating sin is actually the final purpose of redemption. So justification is the ground upon which the progressive defeat of sin is built. In my opinion someone who isn't concerned about sin either doesn't have faith at all or at least has seriously missed the point of Christ dying for them. Faith is more than intellectual belief. It includes a personal commitment, which in this case I'd say includes a commitment to obey. Not the actual obedience, but the basic orientation from which the obedience comes. And 1 Cor 3:13 ff suggests that sins do have consequences in eternity, even if they don't result in damnation.
But there may still be a difference in attitude. I don't feel that I have to get rid of every sin in order to be saved. I feel I'm God's son, and I'm confident that he won't abandon me, even if I sin. But I also know that he cares what I do. And because I love him, and I'm thankful for what he has done, I am committed to following him. Sin isn't just violating an arbitrary set of rules. It actually causes problems. And as a Christian I want to be as good a servant as possible. I'd rather see you take that viewpoint. The point isn't that you should live in fear that your sin is going to damn you. It's that you should love God and your neighbor. And sexual sin indicates a problem with how you think of or relate to women (or men, depending upon the nature of what it is). As a follower of Christ that's something that should concern you. But I'd rather see your attitude be "I want to be as effective a follower of Christ as possible, and I see that I need to develop better relationships with women" rather than "if I don't get rid of this sin I'm going to end up in hell." That's part of why I suggested a positive approach. I'd rather see you ask, "just how should I be thinking of women, and why did God give me the gift of sex in the first place?" rather than "how do I keep from thinking of this thing?" something that sounds a bit too much like "I dare you not to think of pink unicorns for the next minute." Not to mention that I'd like you to focus on Christ and how to be his servant rather than on your sin, although clearly these are related.
Part of this includes assessing what actually matters. There are certain sexual issues that, even if they actually are sins, may well not be the highest priority issue in your life.* If you've ever read Screwtape Letters, one of the things that one of his tempters would absolutely love is to get his victim to obsess about something that, while possibly undesirable, causes them to completely miss more serious problems in their lives, as well as lots of opportunities to serve God just as they are. But this depends upon you there are certainly sexual sins that can really mess up your life, and that of people around you.
Now it may be that this won't always work. E.g. it appears that alcoholics have to be almost fanatical about avoiding alcohol. If you are in a situation that's analogous to that, my comments may not entirely apply. But the concern should still be that alcohol is ruining your life and your ability to do what God intends you to do, and God wants you to be free of it, not that God is going to throw you into hell because of it.
* Note that I come from the liberal side of the Reformed tradition. In my opinion some of the things that people think are sexual sins really aren't. That includes one specific thing that typically tends to bother many (maybe most) teens and young adults. However for purposes of this discussion I'm assuming that what you're concerned about is actually wrong. In some sense if you think it is, it can be a problem for you even if I wouldn't agree.