Prince Otto, Robert Louis Stevenson's Ruritanian Romance, actually predates the form, in its way -- Stevenson publishedPrince Ottoin 1885, where Anthony Hope'sThe Prisoner of Zenda-- the novel set in the fictional nation of Ruritania that gave the type its name -- wasn't published until 1894.
Stevenson calledPrince Otto"my hardest effort," and it may well have been: one of the chapters was rewritten eight times by Stevenson and once by his wife.Prince Otto, an action romance set in the imaginary Germanic state of Grünewald, was Stevenson's third book, written two years afterTreasure Island.