Why Read What We Can't Remember?

Wouldn't it be great if we actually remembered exactly what we read? Which brings up the book I'm currently reading, Jesus Before the Gospels by Bart D. Ehrman. Don't be misled by the title, because the book is about memory and not religion. There were 40-65 years between when Jesus died and when the four Gospels were written. This book is about how historic events might have been remembered and passed down orally. Ehrman explores the limits of memory in a preliterate culture. I'd be in big trouble if I had to write the Gospel According to Jane Mayer fifty years from now.