Shadow Realms: Forsaken Realms

From the introduction:
Shadow Realms: The Forsaken Realms written by Ben Palmer & Len Charlton is an expansion of the Shadow Realms game world, bringing the flavour of the post-holocaust mixed up with the high fantasy of the Shadow Realms setting.
Forsaken Realms is set in the future of the Western Realms, set in the ruins of a modern day civilisation. A once great technological, economical and magical society has been laid waste by unknown forces and the remaining few strive to survive and piece together what brought the Fall so they may find a solution to their Forsaken Realm.
In this new order it seems the survivors deities have abandoned them, technology is dysfunctional and lost. Without the academia the art of magic has become slowly forgotten and the spirits of nature are twisted and perverted by the change in landscape.
All the while demonic forces stalk the lands searching for fresh souls, the dead are restless stirring from their graves, cults rise up to appease their new masters and horrific diseases spread across the ravaged land. After centuries of squabbling the races of the Western Realms have set aside their differences and have banded together to retake and rebuild their world.