It is his first book, Peace with God and is available free through the Billy Graham Evangelistic Association by clicking here.
It is described by the website as
Billy Graham's first—and possibly most powerful—book, "Peace With God," has become a Christian classic. Within its pages Billy shares God’s gentle, reassuring promise of spiritual calm and authentic peace—a precious promise in an age when so many are wracked with too much stress and too many burdens. Since its original publication in 1953, millions have followed its clear, simple steps and discovered for themselves the revolutionary new life found in Jesus Christ. Now reprinted as a special Billy Graham Library Selection, the book points unerringly toward the One who is the only dependable source of the peace that passes understanding. Both comforting and challenging, this explanation of the human predicament and the divine answer has been changing lives for generations.