This account nicely captures Bismarck's "wonderful flexibility of strategy and tactics". His power rested almost entirely on his personal relationship with and psychological hold over king/emperor William I (despite opposition from the rest of the royal family), displayed most prominently in histrionic threats to resign if he didn't get his way. Bismarck's efforts were directed at cementing personal imperial power, and thus his own power, at the expense of pretty much everything else, whether consistency or values or loyalty.
Bismarck combined "shirking responsibility for what went wrong" with "rage and brutality to his enemies". Stress brought on regular bouts of illness and hypochondria and long periods of withdrawal spent largely in bed; Steinberg devotes considerable space to Bismarck's psychology and health. We are also given details of his daily life and many descriptions of meetings with him, but somehow he never really comes to life as a person.
Steinberg offers little background information, pretty much assuming the reader already has a basic grasp of Prussian history and of 19th century European history and politics more broadly. There are some scattered exceptions to this: we get mini-biographies of key figures such as Moltke, Roon, Lassalle, and Windthorst and a potted history of German anti-semitism, focusing on individuals such as Wagner and Treitschke, with an embedded account of the great depression of 1880.
The coverage and depth are uneven in other ways. There is no account of the key battle of Königgrätz, for example, just an analysis of a possible flank attack by the Austrian IV Corps that never eventuated, to support an argument that there was a good deal of luck involved in the Prussian victory and thus in Bismarck's success (though contingency is not dwelt on elsewhere). And Steinberg quotes at length from relatively obscure sources, including letters by minor figures which describe Bismarck. Some of this material is apparently new, but it's not clear that it deserves such prominence in a general biography.
Bismarck: A Life is never hard to read, but does feel rather awkwardly structured in places. A shorter alternative would be the new edition of Feuchtwanger's Bismarck: A Political History which has just appeared.