I can't believe I'd never read these, given how much I love ghost stories. I'm generally not into short stories, but these are tied together nicely through the single narrator conveying stories from his colleagues, all academics making inquiries of various kinds that lead them to the supernatural encounters. The stories are subtle and creepy and hold up well, despite their age. There's even a touch of humor from time to time. The story that had been recommended to me so highly in recent years, "Oh Whistle and I'll Come To You, My Lad," was good, but I think my favorite may have been "The Mezzotint." 
 I don't reread books often, but I plan to revisit these stories again sometime. As much as I love horror as a genre, I lately find myself tacking on the qualifier, "but this is not my thing." These classic ghost stories are exactly my thing. Loved them.