There is also an essay by Sarah Greenough, senior curator and head of the Gallery's department of photographs, on "the idea photography" in which she traces the photographer's search for "objective truth." Greenough recognizes the influence of the modern art he championed in Stieglitz' decision to reject pictorialism and the Photo-Secession and instead embrace "straight" photography. It was Stieglitz' search for abstraction in photography that eventually led him to create his Equivalents cloud series.
There aren't going to be any surprises in a book such as this, but there is an interesting insight into Stieglitz' character in a quote from a letter he wrote to Ansel Adams dated December 7, 1933.
"... You ask what my attitude is. Man can't you figure it out for yourself. I am trying to sustain life at its highest - to sustain a living standard. To let every moment actually live without any ism or any fashion or cult attached to it... I chose my road years ago - & my road has become a jealous guardian of me. That's all there is to it..."
For those interested in a comprehensive biography of Stieglitz, I can recommend Richard Whelan's Alfred Stieglitz for the honesty with which it approaches its subject.