Stop Asking Jesus Into Your heart by J. D. Greear
Stop Asking Jesus Into Your Heart is a great resource for young Christians and/or Christians who have fallen into the "trap" of doubting their salvation.
J.D. Greear walks us through his own personal experiences with doubting his conversion/salvation. His testimony will especially resonate with those who have grown up in an evangelical church (even more so with those from Southern Baptist churches). Greear draws your attention to the (over?)use of Christian lingo in churches like: "walk the aisle", "ask Jesus into your heart", "pray the prayer", etc... It's the consistent use of this kind of lingo that, Greear argues, can not only create a sense of doubt later on down the road, but also lead to "false conversions" where someone "prayed the prayer" or "walked the aisle", but didn't actually become a Christian.
Greear's journey from a state of constant fear to discovering peace in Christ is a great read for anyone at any stage of their Christian walk. I think Greear's journey is something almost every Christian will experience and/or need to go through at some point in their lives - especially those who accepted Christ at a young age. Greear presents the gospel and references Scripture liberally throughout the book as well, giving it a strong and legitimate foundation.
Definitely check this book out.