I am 87% certain that you can only get it from the dev (gets you a steam key) or steam itself.
Q: How much does it cost to play and where can I buy it?
A: The pre-order is already running, you can purchase the game here on our devblog for 15 USD. After its release you will also find it on Steam and XBLA.
Source: Link
At any rate, Gamestop does not appear to sell the game. A product search for "van helsing" only turns up console games and the movie.
Link
It's supposed to be a fun game, it's gotten rave reviews, you should actually buy a copy if you want to play it. Support indie developers. It's 10% off until the 29th, and isn't exactly costly to begin with.
[Edited by Dhampy, 5/27/2013 12:48:27 AM]
ok! I did as you suggested and bought the hunter pack and none of the trainers will still not work, so I just wasted $15 hard earned bucks.
oh and by the way you replyed to your own question, you asked where to get the game and then you provided a link to where you can buy the game. go figure! you must be talking to yourself LOL LOL LOL
[Edited by METALDIK2008, 5/27/2013 5:18:31 AM]