The setting is an alternate history's 1984, where Vicotrian ideas and politics still exist with only slight changes. Ethertech takes the places of both steamtech and cybertech, but blends the two together very succesfully while retaining the best flavor of both. Horror elements do exist, mainly related to the etherscope and in keeping with some of the Victorian era lit, but can be used to the degree that you wish.
Most PCs are baseline humans, but variations exist created by A Brave New World-esque form of eugencis. Cybernetic analogs are also possible. Classes are modifications of the d20 Modern system, only in the sense of progressing through 10 levels with feats and talent trees, but are far more setting specific and flavorful. Two single classed PC of the same base class can prdocue widely different character concepts easilly throgh skil and talent choices. Combine base classes or add in advanced classes for more specific concepts. The game is worth it for social mechancs and fighting styles alone in my opinion.
You can easily play a wide variety of games with just the core book:
-martial arts(seeting wise primarilly in the west, but need not be completly so)
-occult investigators (with or without horror)
-espionage and covert ops
-pulpy swashbuckling adventure (complete with zepplins)
-social and political intrigue
-criminal gangs and organized crime
-cyberpunk (even a whole game spent in the 'scope)
-no doubt many more but it has been a while since I looked at the book.