From the publisher:
Which side will you choose? Which weapons will you wield? Earth is torn between the order of science and the chaos of fantasy. These two worlds cannot mix. Venture into lands once claimed by skyscrapers and factories, now overrun by elves, goblins, and dragons. Choose your path and commit to the quest. Monsters will hunt you; machines will track you. No gods will help you; no prophecies will choose you. The fate of the world rests with you.
This rulebook includes:
New races
Four technology-based classes
Paragon paths for both science and magic based characters
All new equipment from revolvers to railcannons
Listings for powered armor and futuristic vehicles
Monsters for every challenge rating
GSL-compliant rules to add technology to any 4th Edition game