Queen Sheba's Ring, Centennial Edition, 1909-2009, By Sir Henry Haggard

Four men travel into the Sahara in search of the lost kingdom of Mur: an old doctor looking for his lost son, a professor in search of learning, and a young man in search of adventure with his old sergeant. The inhabitants of Mur, the Abati-one of the lost tribes of Israel, now in the decline of their civilisation fallen into effete cowardice and lethargy. Their queen-Maqueda, the Child of Kings, descended from Solomon and the Queen of Sheba, one of the few Abati that still shows courage and enterprise. Their enemies-the warlike and vigorous Fung, who worship the gigantic lion-headed sphinx Harmac. The mission: blow up the mountainous sphinx, thus demoralising and dispersing the Fung and rescuing the Abati people from extinction. Rescue the doctor's son from the Fung. Escape death by lion. And do it all without falling foul of the villainous Joshua, Prince of the Abati, and without falling in love with the spirited Maqueda, for which the penalty is death. More easily said than done..