I picked up Mailer's book on Picasso at Half Price Books for $3. Half Price Books' clearance section is always good for three or four bargains. Mailer was a steal, if only for all the photos and color plates (although they were probably the best part of the book when push come to shove). Mailer's art criticsm tends toward the fanciful flight school.
As far as the details of the painter's early life are concerned, Mailer does a lot of lengthy quoting from contemporary sources and modern critics. While contemporary accounts are intersting, they aren't always very reliable.