Hitler: Ascent, 1889-1939 by Volker Urlich, 998 pages.
Ullrich provides a very thorough, well-researched account of Hitler's life, and his rise to power in twentieth century Germany.
I haven't read Ian Kershaw's or Alan Bullock's accounts of the megalomaniacal dictator (though I did read Bullock's 1992 Hitler and Stalin: Parallel Lives, which was fascinating), but it is easy to believe that this work appears to be their equal. Ullrich is dispassionate, and shows the human side of Hitler, letters and diary entries of those who knew him and found him charming, but always lets the reader know how that charm was balanced out. Hitler seemed to love no one, at least not enough to leave a clear impression on anyone. If he loved his niece, Geli Raubal, her suicide marked it as a love of the creepiest kind. If he loved Eva Braun, then their very strict privacy, their joint suicides, and the lack of surviving letters between them, left no witnesses to that love. If he ever felt true compassion for anyone in the world (anyone non-Aryan anyway), then his duplicity, his manipulating those around him, his false words, and false acts ensured that no one knew of it.
An important book. A detailed account of how lies, lust for power and revenge, and complete lack of human feelings can lead one man onto the world stage and how the misreading of a leader and strange, strange political events can lead to destruction on an enormous scale.