This movie is EXACTLY what is sets out to be: a live-action retelling of the Crooked Man story from the comics. It doesn't have a budget in the tens of millions, Hellboy isn't depicted as an quippy action hero (because he isn't in the comics), and it's appropriately dark and eerie. Mignola himself had a hand in creating it, and I thought it was delightful.
People who gave this movie a negative review fall into two categories:
1. They don't know Hellboy and are upset because there wasn't a lot of preliminary exposition and hand-holding.
2. They only like big-budget movies with lots of special effects and smooth transitions and drama. This is an indie movie and it never pretended to be anything else, so giving it a negative review on this basis is like going into a burger joint and throwing a tantrum because they don't serve foie gras.
I applaud this movie for being true to the source material and true to itself. It was very enjoyable. =)