From the New York Times:

Robert K. Massie, a Pulitzer Prize-winning biographer who wrote gripping, tautly narrated and immensely popular books on giants of Russian history, died on Monday at his home in Irvington, N.Y. He was 90.

The cause was complications of Alzheimer’s disease, said his wife, the literary agent Deborah Karl.

In monumental biographies of Peter the Great (1672-1725), Catherine the Great (1729-96) and Czar Nicholas II and Czarina Alexandra, who were assassinated with their five children and others in 1918, Mr. Massie captivated audiences with detailed accounts that read to many like engrossing novels.

I’ve read only one of his books: Dreadnought: Britain, Germany, and the Coming of the Great War (1991), which I enjoyed. The article claims that:

Some criticized Dreadnought as lacking disclosures from original materials — a regular criticism of Mr. Massie’s reliance on secondary sources — but others praised his dramatic description of a grand failure in crisis management.

But that was not the impression I got when I read the book; in fact, I thought that he relied too much on extended quotations from letters, speeches, or telegrams, etc. (Yes, primary sources are important, and some of these make for good reading, but I’ve always thought that it’s bad form to quote them repeatedly and at length – exert some power over your sources and incorporate their ideas into your own prose.) Otherwise, the book was quite compelling, and it was fascinating to learn about such people as Kaiser Wilhelm, Bismarck, Holstein, Eulenburg, or Hohenlohe; and on the other side Queen Victoria, Lord Salisbury, Joseph Chamberlain, Cecil Rhodes, the young Winston Churchill, Herbert Asquith, Jacky Fisher, or David Lloyd George, and about the process by which Nelson’s Victory was transformed into Fisher’s Dreadnought. Those two strands never really come together, and the book doesn’t even end with the Battle of Jutland, but it remains an engaging portrait of that important period of European history parallel to Barbara Tuchman’s The Proud Tower (1966).