...and some were really quite enjoyable. Did he write these or was it his "stable"?
Unfortunately, they're written by his "stable:" a guy named Justin Scott, who's listed as a "co-author." I have read the first five, and the series is enjoyable enough, but the characters are definitely on the one-dimensional side of the spectrum. And yes, they would be fine for a pulp league if you move them and their equipment into the 20s/30s/40s or whatever pulp is to you.
The Bell series actually was the basis for my very first effort at authoring an In Her Majesty's Name company (where I moved them
back a couple decades), found here:
http://wrgmr.com/van%20dorn%20detective%20agency.pdfThe descriptions of the characters in my IHMN company PDF are right out of the books, except for some minor details (note the disclaimer at the end).
The only truly recurrent characters are Isaac Bell and his true love Marion Morgan; the rest come and go, and some are simply killed off.
Great idea for pulp, though, warrenbruhn, one that hadn't occurred to me!

Isaac the Leader, Marion the Sidekick, the other named Characters as Allies, the nameless detectives as Followers.....should work well!