Anthony Hope 
Prisoner of Zenda 

Disaster strikes when the king of Ruritania is drugged on the very eve of his coronation. The ceremony cannot move forward without him — and if his power is not made official, those scheming to seize the throne for themselves may move upon it. With those loyal to the crown desperate for a way to stall until the king is safe once more, a visiting Englishman with a startling likeness to the monarch is convinced to take his place — and must now work against the forces plotting behind the crown’s monarchy’s back.