Own the series and think it's pretty good, haven't rewatched it in a while though. I don't know if I'd consider it super spooky besides maybe the last arc (Bloodstained Labyrinth) which I remember freaking me out a bit, you're in it more for the fun cast exploring haunted places. Series also has a pretty memorable Christmas episode because I still get depressed thinking about it, that and the last arc are the stand outs in my opinion. Don't know if it makes a difference, but I only ever watched it dubbed since it was one of those early anime I got into, which I found pretty decent and would recommend checking out if possible.
Slow paced, but I think you'll have fun if you like those paranormal investigation shows since it apparently captures that pretty well. Think it does a pretty good job capturing atmospheric horror with the different places they investigate. Only big negative I can think of is the usually problem with adaptions that don't have the time to go as in depth as the source material, coupled with it likely never getting a second season. Thankfully it seems that the
LN got fantranslated, might check it out myself, since it's completely translated.
Also has a pretty spooky main theme:
https://youtube.com/watch?v=2XL128AEniM