In our experience the following books are the best on self-worth and significance issues.
Faith Therapy: Probably the most specific book on overcoming self-worth and significance issues.
Transformation: Has a complete chapters on overcoming inferiority and feelings of abandonment.
Search for Significance: The classical book on this issue.
Root of Rejection: The effects of rejection and the answers for recovery.
Approval Addiction: The trap of basing one's worth on the approval of others.
The power of Right Believing: Overcoming fear, guilt and addiction by understanding the unmerited favor and love of God for us based on what Christ has already accomplished on the cross.
Destined to Reign: Our ability to reign in life is not based on our performance but on what Jesus had done on the cross and has freely given us and the gifts of righteousness and of no condemnation.
Unmerited favor: All that is required to receive God's unmerited favor is to receive his free gift of grace and realize that we do not merit it. He loves us unconditionally and has already forgiven us based on the fact that Jesus took the punishment for all of our sin and given us the gift of His righteousness without works on our part.