Identify series of books about a kid and older man who fight supernatural creatures

Question

I originally read these books in the late-80s. I believe, but am not sure, that new novels in the series were still coming out at that time.

They were full novels, and there was a series of them. At least three, but probably more. The hardcovers had spooky looking hand-drawn cover art, which was mostly black & white with maybe a small splash of color. While the books dealt with supernatural horrors, they were young-adult books and probably couldn't have been too gruesome or scary, because they were available at the elementary school library.

The main character was a boy who I think was probably around age 10-12. There was also an adult (possibly elderly, and I want to say a professor) who got into adventures with him. The books dealt with them fighting supernatural creatures. The setting was the real world (though, obviously with supernatural elements), but I'm not sure of the time period. I think it was set maybe in the Victorian era, but it's also possible it was set in somewhere in the 1940-1960 range. I know it was definitely at least pre-1980 in terms of time period, as the setting seemed "old" to me when I read it as a kid in the 80s.

Answer 1

I'm pretty sure it's the Johnny Dixon Mysteries by John Bellairs.

The covers of early editions were illustrated by Edward Gorey, who has a very distinct (and faintly morbid) style.

They were, I believe, set in the fifties, and dealt with the adventures of a boy, a Professor, and (later on) the boy's friend, fighting ghosts, demons, and the like. They were terrifying. I loved them.