Quadruple-biographies are difficult to pull off, but Nancy Goldstone's done a worthy job with Four Queens: The Provençal Sisters Who Ruled Europe (just out in paperback from Penguin). Goldstone's subjects are Marguerite, Eleanor, Sanchia and Beatrice, the four daughters of Count Raymond V of Provence who became the queens of France, England, Sicily and Germany.
In the tradition of Alison Weir and Antonia Fraser, Goldstone has written a richly-narrated popular history focused squarely on the influences of the women she views as being at the heart of medieval Europe's political, religious and social culture. Some of her divergences are just as interesting as the main narrative (which alternates between the sisters in a smooth and effective way).
I must fault the book for its total lack of footnotes, especially since - as Goldstone notes - several of her characters have not been the subject of recent biographies. The illustrations which accompany the text are somewhat useful, although I found the maps too stylized to be of much use. I had minor issues with some anachronistic thinking that crept into the text, and a few of Goldstone's glib generalizations bothered me, but on the whole this was an engaging casual read.