I have lots of music heros, but Van Ronk and Oscar Brown, Jr. have ranked one and two since I was in junior high school (I am now 62). Of course, I am biased in favor of this book...I often pick it up and read a chapter here and there. Highly recommended.
Another fun book of this time is: Hoot! A Twenty-Five-Year History of the Greenwich Village Music Scene. This "history" is a collection of thoughts by many of the the people who were there. I passed it on to a friend, but it may be time to look for another copy on eBay.
Also, different topic, but David Honeyboy Edwards' book - The World Don't Owe Me Nothing - is a must for country blues fans, as he has first hand accounts of times spent with so many of the masters.