Last year one of my favorite books was The Grace and Truth Paradox by Randy Alcorn. This year, I read another book from his Lifechange Books series - The Purity Principle.
The Purity Principle is simply this:
"Purity is always smart; impurity is always stupid."
This was not the first time I had read this book, and it probably will not be the last. It was encouraging and convicting to come back to this book after reading it five years ago and see what the truth and wisdom laid out in this book has reaped in my life since then, and see areas in which I still need to grow. The Purity Principle (both the book and the actual principle) is Biblical and practical.
This book finds the perfect balance between being theological and being practical as well as being frank but not gratuitous in it's detail.
This is THE book I recommend to those struggling in the area of purity.