Passion & Purity

I have not read this book personally (Yet, but have my own copy now!) but have heard nothing but good things. I would recommend to any young person to read a book such as this. I believe it important for young people (including myself) to glean as much as possible from those older and wiser than we; it will prevent a lot of heartache in the end and avoid many troubles.
Here is the description from the back cover:
In Passion & Purity, Elisabeth Elliot emphasizes the need to commit daily to Christ all matters of the heart and to wait upon Him. She teaches this often painful yet rewarding discipline by candidly tracing her love story with Jim Elliot as evidence that she has been there.
Through letters, diary entries, and memories, she shares the temptations, difficulties, victories, and sacrifices of two young people whose commitment to Christ took priority over their love for each other. These revealing personal glimpses, combine with relevant biblical teaching , will remind you that only by putting your human passion and desire through His fire can God purify your love.
Passion & Purity gives honest direction in such areas as:
~ Loving passionately while remaining sexually pure.
~ Whether or not to marry, and who is the right one.
~ The man's and woman's roles in relationships
~ Putting God's desires ahead of personal desires.
~ How far is too far, physically.

Here is a snippet from the foreword by Joshua Harris as well:

"The book you're holding tells a very moving love story. It's honest. It's practical. But even as it addresses the real questions and concerns of single men and women it always lifts our gaze upward - above our immediate preoccupations, above our longings for human companionship to the Maker who created us for Himself."