Only God creates; I assemble. - George Balanchine
I was recently asked to suggest a good book on Balanchine. The first book I'd recommend is Garis' Following Balanchine (for reasons I explain below). Unfortunately, there are no exceptional biographies of him that combine thoroughness with insights; so far, all the biographies written about him have been no more than serviceable. Of those, Robert Gottlieb's George Balanchine: The Ballet Master (2004), part of Harper's Eminent Lives series, gives perhaps the best brief overview. Gottlieb knew Balanchine for several years and was on the board of directors for NYCB, and he's respectful, sensitive, and engaging about his subject. A more thorough book, though not more insightful, is Bernard Taper's Balanchine: A Biography (reprinted 1996), some parts of which were written and published while Balanchine was still alive and able to confer with Taper. (One can read a "brief" 4 part biography of Balanchine here.)
IMO, the best book on Balanchine, the man, is I Remember Balanchine: Recollections of the Ballet Master by Those Who Knew Him (1991), edited by Francis Mason, a collection of 85 interviews from people who knew him. If one wants to know how Balanchine impacted the lives of those he came into contact with and how he was frequently several different personas to many different people, this is the must-read.
Balanchine's own opinion, told to Taper after reading a copy of Taper's biography: "You've written too much about me, and not enough about my dancers."
And so, there are the autobiographies of dancers associated with him: wives Tamara Geva, Alexandra Danilova, Vera Zorina, and Maria Tallchief have all written autobiographies. (Tanaquil Le Clercq, Balanchine's fourth or fifth wife, depending on whether his common law marriage to Danilova is counted, never wrote an autobiography and largely refused to speak about her life with Balanchine. A prominent ballerina at NYCB in its infancy, they married in 1952, but in 1956 she contracted polio and remained paralyzed from the waist down for the rest of her life. After setting aside his work and diligently caring for her for almost two years, he returned to NYCB and in fast succesion choreographed Agon, Stars and Stripes, Gounod Symphony, and Square Dance. They separated after he fell in love with Suzanne Farrell - and made it known to the whole world - and they divorced in 1969.) Dancers Barbara Milberg Fisher, Jacques d'Amboise, Edward Villela, Allegra Kent, Suzanne Farrell, Peter Martins, Merrill Ashley, Toni Bentley, and Gelsey Kirkland have also written autobiographies in which he plays a prominent role.
Of these (so you have no doubts that I have indeed read every single book about Balanchine that I'm referring to here and plenty more than I'm not including), Milberg Fisher presents a fascinating account of life as a corps member and soloist in the first decade of NYCB; Kent's is the wittiest and most "out-there." Gelsey Kirkland's is probably the most famous and the harshest - her Dancing on My Grave (1986) practially (and completely unfairly) lays at the foot of Balanchine her eating disorders, obsession with plastic surgery, and drug addiction, and she was undoubtedly still very unstable when this book was written; however, she and Villela provide the few dissenting voices among the many, including his wives, who describe him as a near deity. And Suzanne Farrell's is, of course, my favorite.
If one is interested in the music angle, Charles Joseph wrote Stravinsky and Balanchine: A Journey of Invention (2002), about the artistic collaboration of these two geniuses (warning: a good knowledge of music is recommended for reading this book), and Balanchine's own opinions on Tchaikovsky and other Russian composers, the St. Petersburg of his childhood and the Revolution, Russian writers, Diaghilev and the Ballet Russes, and other topics are contained in Balanchine's Tchaikovsky: Interviews with George Balanchine (1985) by Solomon Volkov. This book is invaluable if one wants to hear Balanchine's "voice" and ideas on the arts near the end of his life. If one wants to hear Balanchine's actual voice, watch Balanchine.
If one is interested in Balanchine's choreographic output and wants to learn the impact of his work and his dancers on the life of a member of the audience (who was also a music critic and professor of English), Following Balanchine (new ed 2006) by Robert Garis is required. I'd probably read this book and Gottlieb's brief biography in tandem, to gain a hold of Balanchine's background and his creative output at NYCB through the eyes of an audience member. This book is also the must-read for anyone who believes that one's life can be profoundly affected through art and wants to understand why Balanchine's work mattered so much to people; as one NYCB audience member of the 1960s and 70s wrote, "Balanchine was our God and the State Theater was where we worshipped." (Balanchine himself would not have wanted to be called God, though he did once say, in response to why he only had the title "Ballet Master" at NYCB, as opposed to artistic director or head choreographer, etc., "God doesn't have to call Himself God.")
Unfortunately, no biographer has been able to crack the enigma of Balanchine, the man and the work. Ballet fans have been waiting over a decade for eminent dance critic Arlene Croce's promised study on Balanchine and his work. Part of the problem is certainly that Balanchine himself was not interested in introspective self-analysis and even to those close to him he was impenetrable. Whether because he was a life-long adherent of the Russian Orthodox Church or he had a massive ego and was utterly secure in his own choreographic genius - though he would be the first to point out that God gave him his gift for choreography and God told him, "This is the only thing you're going to be good at" - or he followed his judgment alone: "I like what I like and I disagree with everyone and I don't care to argue." A slightly more self-deferential quote in response to a question about the hows and whys of his many marriages and affairs and how it tied into his artistic output: "I am a dancer; I lead a dancer's life. It's like a horse. No one asks a horse what he does - he just leads a horse's life. That's what I do."