Yes, I've read them all...twice now. I actually wrote an article a while ago on Seabury Quinn and Robert E. Howard: [
onanunderwood5.blogspot.com]
The de Grandin stories...are not Quinn's best work. They are not exactly formulaic, but they were novellas starring the same protagonists, and they would have been read no more than one per month, sandwiched between other things, with no common working mythology and little real character growth, making them immediately accessible to new readers. You can basically pick any of the 93 de Grandin stories up and read it as a standalone work. Most of the occult threats are fairly familiar (ghosts, vampires, and werewolves predominate of the familiar fare), with quite a bit of weird crime stuff thrown in, often including some exotic element involving foreign cults or religion or the trappings of the supernatural, and a minority are straight shudder pulp material. A few of them include some more exotic threats, but nothing along the lines of H. P. Lovecraft or Clark Ashton Smith's alien horrors.
Trying to read the de Grandin stories sequentially, one after another, and the amount of repetitiveness quickly becomes wearisome. The nature of the stories requires de Grandin's Watson-esque character Dr. Trowbridge to remain ever critical and unbelieving, even if this is technically the third or fourth vampire and twelfth ghost he's seen de Grandin battle. De Grandin himself is obsequious to the point of being annoying, and more bloodthirsty than Robert E. Howard's Conan the Barbarian: there is no such thing as a returning villain in the de Grandin stories, because every single threat either ends up dead or exorcised, sometimes both. With prejudice. De Grandin also lacks much in the way of standard toolkit - one story will have certain herbs used against a vampire, another story will use completely different plants. Sometimes, this is amusing: de Grandin has destroyed a demonic kitten with a blast of silver filings from a shotgun, defeated a ghost with a vacuum cleaner, and anesthetized a vampire with morphine before driving a stake through her heart and cutting off her head. The very pulpishness of the de Grandin tales can be endearing.
...but also wearisome. There's also a
lot of cringeworthy racism in here - not usually in the sense of Quinn claiming such-and-such a race is inferior, including hefty doses of Yellow Peril, evil Haitians and Africans in voodoo and leopard cults contrasted against smiling and subservient African-Americans, ethnic stereotypes by the pound, stuff like that. There is also one incredibly annoying story where de Grandin literally suggests sending the KKK against a voodoo cult that makes me pissed just to think about it...but it's important to understand that kind of thing (well, not the KKK, but the rest of it) was relatively common and fair game in
Weird Tales of the period.
Which is really the main reason to read the stories: to get a better appreciation for the fiction that was popular back then. Seabury Quinn was the most popular author in
Weird Tales during its initial run, and de Grandin was his most popular creation - with over a million words to his adventures. The first de Grandin fanfiction was published in
1934. That's almost unprecedented - and if Lovecraft boohood de Grandin as cheap sensationalist hackwork, Robert E. Howard enjoyed his adventures. The later de Grandin stories also overlap, very slightly, with the work of Manly Wade Wellman; Wellman and Quinn made reference to each other's characters in their respective occult detective stories in
Weird Tales, so if you like Wellman's Judge Pursuivant or John Thunstone stories, the little throwaways might be a treat for you.
So...I wouldn't say they're
not worth reading, but if you're reading just for pleasure, you might want to take it very slowly, and maybe cherry-pick the better stories like "Ancient Fires," "The Chapel of Mystic Horror," "The Bride of Dewer," and "Clair de Lune," or the more important ones from a pulp-history standpoint like the serial "The Devil's Bride" or "The Jest of Warburg Tantavul."