Hello Sharon
I can imagine that all the different opinions are not helping, and I'm not sure this post will help either... But here's what comes to my mind.
1. Robert Trail's Sermons on Hebrews 4:16, and his sermons on Galatians 2:21. I feel that Mr Trail had a wonderful understanding, and a wonderful way of explaining the freeness of the grace of God. I'm always refreshed reading him, because he does not excuse sin, or our backsliding, but rather directs us immediately to the grace and forgiveness of God. And I learn again and again that spiritual progress can't be made until we have the actual belief of the freeness of God's grace in our hearts. I trust I always have the belief of this doctrine in my head, but it's when I experience the power of it in my heart that I feel the desire to serve Christ the Lord, and to mortify the sin within. And I guess that's why I like Trail so much.
2. Although I haven't even read the whole of it, I would strongly recommend John Owen's work on Psalm 130. He takes a systematic look at what evidence we have that there is forgiveness with God. This might seem strange at first, but as you read it I think you'll realize what a profound effect it has on you. To see in order all the ways in which the Lord has declared forgiveness by way of atonement, I think it will leave one speechless.
3. I read most of Thomas Boston's Human Nature in its Fourfold State when I was 15 and 16, so it's been a while. But I would strongly recommend it. My wife tells me that it was by means of this book that she finally came to understand original sin.
4. Last but not least, we should never forget that little work The Christian's Great Interest by William Guthrie. John Owen himself said "That author I take to be one of the greatest divines that ever wrote. His book is my vade mecum. I carry it always with me. I have written several folios, but there is more divinity in this little book than in them all."