In A Lonley Place: Classic? Why? (Spoiler?)

Just saw IALP for the first time. Thought it was o-k and would watch it again, but without telling too much, it would seem we are supposed to sympathize with the protagonist (Bogie) but to me that's a little hard in this case. Not that I dislike him, but it always points to him going psychotic at some point, so perhaps it's Gloria Grahame we are supposed to be invested in?
The story IS pretty vivid and interesting to follow, maybe a little slow in the middle (the writing scenes and at the piano), but as he begins showing his true colors and the movie starts wrapping up, I was just glad GG wasn't hurt in the end.
Was it supposed to have a lot of tension, like a Hitchcock film? I suppose it did.
I liked it o-k, but I'd be curious what others think about it.