OK, maybe not, but his books were the first time I heard about the mystical traditions associated with the urim and thumim, about the Blood of Hailes, and a lot of other things that are not part of the modern school curriculum. Which tells you that Bellairs did not write down to his young readers.
I first encountered his books either through the PBS TV show Once Upon a Classic or the Saturday morning book dramatizations on one of the Big Three networks. It was The House with the Clock in its Walls, which was published in 1973. I remember it being creepy and cool, the story that is. I didn’t read the book until later, and then to my delight, the public library had a lot of Bellairs’ books with the Edward Gorey covers and interior pictures. (I met Gorey through Mystery on PBS, and then crossed paths with his Odder work here and there.) Bellairs had three main series for younger readers, all of which were Gothic mysteries with a touch of horror, and all of which I enjoyed. I suspect that’s where my “eccentric relative of main character with esoteric knowledge” sort of characters originally came from.
His three main young reader series all feature a boy and either an eccentric relative (uncle who just happens to be a wizard) or mentor (Miss Eels the librarian in the Anthony Monday books; a slightly odd professor in the Johnny Dixon stories). In each case, something has happened to the boy’s parents that either they are out of the picture (death, deployment to Korea for Dixon, financial problems so that the boy has to work for Anthony Monday). The boys rise to the occasion with some help from their mentors, and from minor characters with even more eclectic knowledge. There is spiritual danger, physical risk, mystery, all sorts of neat stuff. Evil is punished, and the merely irritating get what they deserve.
Through the books, I learned important things like, oh, how to make a Hand of Glory (please don’t try this at home), what certain relics might do, how the gems of the High Priest’s ephod related to the Ark of the Covenant (don’t try that one at home, either), the joys of dropping a drawer of a card catalogue (which I knew already, alas), and so on. Granted, some of those were probably not all that relevant to a kid growing up in the Great Plains, but one never knows.
I highly recommend the original books, those written between 1973 (House with a Clock in its Walls) and 1991. Bellairs died young, and although others have finished his existing manuscripts and expanded some of the story ideas, the reviews for those are mixed, and I have not read most of them. His adult stories are also dang creepy, well written, and fascinating.
*It turns out I was not far from Hailes Abbey. If only I had known . . . Roslyn Chapel had to suffice my itch for the Esoteric. (Go for the Katherine Kurtz stories. Skip Dan Brown. Please.)