The main difference is the setting, the modern world. Its not a class system but a wheel where you choose abilities. It feels fresh and free.
First time you might be puzzled that you can only have 3 quests. I have always been annoyed about my quest log getting full. Here 3 quests feel right as its hard to investigate more than three things. It also make you live yourself more into the story.
I think this game havent dumbed itself down to please the masses, but instead walked its own way. Some might find it offending, during suggestions of sex,drugs and rocknroll others will love it for the same reasons. Funcom made huge errors when they released Conan, but its four years ago, and it seems they have learned a lesson or two.
Cya in the secret world....