It used to be easy to draw up this list. There were always a few books that sold enough copies through the Royalty.nu site (and this companion blog) to be identified as the World of Royalty's bestsellers. Recently, however, it's become less common for a single book to sell more than one or two copies in a two-month period according to the reports I receive from Amazon.com.
But three books made it onto this last bestseller list for 2015 by selling three copies apiece (woo hoo)! Those books are (in alphabetical order):
A Day With Marie Antoinette by Hélène Delalex. This slipcased volume features personal correspondence, illustrations, and a wealth of unpublished material about French queen Marie Antoinette.
Emperor Hirohito and the Pacific War by Noriko Kawamura. Traces Japanese emperor Hirohito's actions from the late 1920s to the end of the Second World War.
Kamehameha III by P. Christiaan Klieger. A biography of the Hawaiian kingdom's longest-ruling, most beloved, and most defiant king.
For 2016 I will try making the bestseller list quarterly instead of bimonthly. I hope over the next three months publishers will give us some exciting books on royal themes that can become World of Royalty bestsellers!