H. Rider Haggard 
Allan and the Ice Gods 

This novel is the final volume of the Allan Quatermain saga, and it comprises the fourth part of a loosely linked series begun with Allan and the Holy Flower. Once more Quatermain takes the hallucinogenic taduki drug, as he did in previous novels, and he relives a previous incarnation. He finds himself in pre-historic time, ‘cave-men’ times, and enjoys a variety of adventures.