In English, check out:
Benigsen, George M. "Year of 1917 in the history of the Russian church." St Vladimir's Seminary Quarterly
7, no. 3 (January 1, 1963): 115-132.
Bogolepov, A. A. Church reforms in Russia, 1905-1918, in commemoration of the 50th anniversary of the All-Russian Church Council of 1917-1918
. Trans. A. E. Moorhouse. Bridgeport, Conn.: Publications Committee of the Metropolitan Council of the Russian Orthodox Church of America, 1966.
Also, check out Vols. 5 and 6 of the Collected Works of Fr. Georges Florovsky. These volumes contain a translation of his famous Putì Russkago Bogosloviya
(Paris, 1937). While the Sobor only plays a small role, Florovsky's work definitely has unique content and explains the situation leading up to the Sobor.
P.S. I've never read it, but just found this one too: Cunningham, James W. The gates of hell: The Great Sobor of the Russian Orthodox Church, 1917-1918
(Minnesota Mediterranean and East European monographs), 2002.
You can download a pdf of the book's introduction here: http://www.dyrud.org/IntroGatesofHell.pdf