Edgar Rice Burroughs 
Tarzan, Lord of the Jungle [EPUB ebook] 

In this classic fantasy adventure, a rescue mission leads Tarzan to a dangerous lost civilization of medieval knights. Deep in the jungles of Africa, a party of evil slave traders search for the Leopard City of Nimmr in the Valley of the Sepulcher, where they hope to find treasure. Stumbling in that direction is a lost American photographer, James Blake, whom Tarzan has vowed to rescue. But the valley holds more than treasure. Centuries ago, a group of Knights Templar got lost on their way to the Holy Land and became shipwrecked. Now they are ready to continue their Crusade, armed with lances, swords, shields, and pikes. Soon Blake finds himself in armor, fighting for the honor of a princess, and Tarzan prepares for battle. That is when the slave traders strike!