This was the first Mario Bava film I watched as well. I was lucky to pick it up when Suncoast had many Anchor Bay titles for 2.50. It felt a little cheesy sometimes, but overall, it creeped the hell out of me, which doesn't happen very often. I still marvel at how effective the shot where the kid is running down the hall and then the man pops up instead. One of my favorite shots in any horror film.
So now who is going to release a fancy-schmancy version of "Shock/Beyond the Door II" that I can display between my Arrow and VinSyn editions of the other two movies in this loosely strung together series??...I think "Shock" might be my favorite of the three