Lori had "Gus Was A Friendly Ghost" when we were kids, and I always loved it. I was so happy when I found a copy for myself! (She still has hers.)
I like to collect these old Scholastic books whenever I find them, and I put some of them out with my Halloween decorations:
"Mystery At Shadow Pond" looked especially familiar - so we either had it, or I knew someone who did:
Mysteries and ghost towns and frightening masks for secret hide-outs!