The interface for Van Helsing is about what you would expect for an action role-playing game. The camera gives you an isometric view of your surroundings, and the left mouse button does the bulk of the work, allowing you to move, attack, and pick up loot. You can also use the right mouse button for a secondary skill, press the Q key to quaff a healing potion (all of the healing potions are the same, so a single key is enough), press the R key to switch between melee and ranged attacks, and press the shift key to attack without moving.
What you do in Van Helsing, for the most part, is kill stuff. During the early part of the campaign, you encounter bandits, werewolves, mechanical men (who look a lot like British redcoats), harpies, and more. You also talk to people to pick up quests and purchase equipment, which sometimes requires you to make decisions. For example, at the end of one quest, I had to make a choice about killing or freeing a werewolf. I decided to let him go, and later I got a reward because of it. I also saw some places where I had to choose what to do with quest items, where different actions give different rewards.
So far I'd say that The Incredible Adventures of Van Helsing looks pretty good. I liked the theme of the game, with fighting evil creatures in dark caves and forests, and I also enjoyed the rapport between Van Helsing and Katarina, who have amusing conversations with each other. I didn't see much of the main storyline (you receive a plea for help from somebody in Borgova, but I was still on my way there when the preview build ended), and so your ultimate goal in the game is still a mystery, but I'm optimistic that it will be fun and surprising based on the writing samples I've seen so far. Look for Van Helsing to be released at the end of this month