"Forgotten God" is a book written by Francis Chan that explores the role of the Holy Spirit in the lives of Christians. Chan emphasizes that many believers overlook the importance of the Holy Spirit, focusing instead on God the Father and Jesus Christ. He encourages readers to develop a deeper relationship with the Holy Spirit, who is often seen as the least understood member of the Trinity. The book combines personal anecdotes, biblical teachings, and practical applications to inspire readers to recognize the active presence of the Holy Spirit in their daily lives. Chan aims to rekindle a sense of awe and reverence for the Holy Spirit, urging believers to seek His guidance and empowerment.