As someone who was very excited to understand the background to the Nag Hammadi find, I was disappointed that this account was fairly limited. It glosses over the period of translation and presents a dated view of the contents of the codices themselves. This perhaps was the greatest letdown of all - this is a reprint of a 1958 publication. If you are seeking new information and analysis on this topic then I would consider Elaine Pagel to be my reference of choice.