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.