G.A. Henty 
Knight of the White Cross [PDF ebook] 

For centuries, the island of Rhodes had been the territory of the Knights of Saint John, a military regiment with ties to the Crusades. After a failed invasion in the late 1400s, the Ottoman Empire launched a second campaign to take back the strategically important island in the eastern Mediterranean. In this exciting account of the conflict, a young knight named Gervaise Tresham does his best to defend the island.