The Night Land is a wonderfully imaginative, yet starkly creepy novel written by William Hope Hodgson in 1912. Imagine a world, millions of years in the future, where the sun has gone dark, and a cold, stark Earth is lit only by residual volcanism. What's left of mankind, about five hundred thousand of us, cower behind a force field, in a great arcology called the Last Redoubt. All around are monstrous things, some alien, some once human, and some that very nearly defy categorization.
Mankind is a dying breed, no longer adapted to exist in the black hell that the Earth has become - but some things endure, even across the ages. Somewhere in 17th century Earth, a man is separated from his love, and loses himself in mourning. He then has a vision of this bleak, shadowy future. At this point, the reader's vantage point shifts to that of one man, X, living in the Last Redoubt. Mankind in this age is gifted with at least limited telepathy, and through this, X hears one voice, all alone in the night. He knows that this voice belongs to the soul of his lost love, whatever form she might be in now, and he sets off into the shadows to find her.
There is so much more to this story, but I shan't give spoilers here. The copyright on this book has expired, so now it's within the public domain, and can be obtained freely and legally on the internet. * Anyone who's a fan of dark yet hopeful fantasy, or of bleak horror, owes it to themself to give this book a good read.
*Yes, even with the author's life plus 70 years extension. William Hope Hodgson, alas, was killed in 1918 while fighting in World War I, and as such, even the extended copyright on The Night Land expired in 1988.