The time machine - H G Wells

When a Victorian scientist propels himself into the year 802,701 AD, he is initially delighted to find that suffering has been replaced by beauty, contentment and peace. Entranced at first by the Eloi, an elfin species descended from man, he soon realises that this beautiful people are simply remnants of a once-great culture - now weak and childishly afraid of the dark.
They have every reason to be afraid: in deep tunnels beneath their paradise lurks another race descended from humanity - the sinister Morlocks. And when the scientist's time machine vanishes, it becomes clear he must search these tunnels, if he is ever to return to his own era.