Man and the Sun by Jacquetta Hawkes.

This book is about mans relationship with the sun, primary in the form of solar worship from ancient Babylon, through Egypt, the Roman Empire and up to modern times.  Hawkes covers the subject well, though sometimes fails to distinguish between those who worshiped the sun as god and those who considered the sun a symbol of God.  Unfortunately, this book is no longer in print and must be purchased used.