It comes close to capturing the tone and atmosphere you'd get from reading H.P.'s best. Its slow build up of tension, the body-warping phenomena, and the late-stage insanity are all done very well. It's close to being the ideal adaptation, but a few things hold it back.
The most obvious one would be our good 'ole boy, Nic Cage. He didn't go fully insane here, or commit to his character either. He seemed like he couldn't make up his mind on taking this role seriously or not. You could chalk his behaviour up to the effects of "the color," but it just seemed like an inconsistent performance to me.
The second thing would be the meandering plot. I know the story is supposed to follow the day-to-day lives of this family, but the series of events didn't feel organic. What I mean is that it sometimes felt like things were happening only because the script said so.
Regardless of these critiques, this is still the best adaptation old Howard has gotten. If you haven't seen it already, smoke something and delve into this movie's madness. This one is a Good.