What is Surprised by Joy about?

In his book titled "Surprised by Joy: The Shape of My Early Life", author and thinker C.S. Lewis sets out to describe the ways in which his childhood and education shaped his mind and trained his thinking to lead ultimately to his concluding that Christianity was the most valid and comprehensive answer to his inherent longing for the experience he calls Joy. He follows the thread through his youth and into adulthood as he experiences Joy, first in his imaginary and literary world, later in nature. Finally, after long searching for joy intellectually and aesthetically, those searches pointed to the transcendent Source and Author of joy, the God of Christian scripture.