I bought Austin Hall's novel The Spot of Life (published serially in 1932 and first printed in book form in 1964) because it was only a dollar and it had this quote on the back: "But nobody had reckoned with the cunning brain of the ruler of that Other World, the weird warrior-king known as the Bar Senestro." Just say "Bar Senestro" a few times. Now don't you want to read it too?
When Detective Flanning sees an oddly dressed but very handsome man walking down the street in San Francisco, his curiosity overtakes him and he offers to show the man the way to an address he has written on a scrap of paper (the home of a professor and Spinoza scholar). The stranger causes quite a scene with the professor, so Flanning then follows him to a mysterious house that has given off weird vibes to everyone in the neighborhood for thirty years. After Flanning enters the house, things really start getting weird: Strange lights flash, bells toll, odd people are alive, then dead, then disappear completely. Then the Spinoza scholar is found dead, and Flanning finds himself teaming up with the professor's son -- a science whiz who is also the captain of the college football team. Together they hope to solve the mystery of the weird spot in the mysterious house, learn a few things about Life and Death, and save humanity from an inter-dimensional invasion.
Although it didn't mention anything about it on the cover of the book, The Spot of Life is actually a sequel to The Blind Spot, which Hall wrote with Homer Eon Flint and which was serialized in 1921. Flint died in 1924 under mysterious circumstances (he may or may not have been involved in a robbery and may or may not have been killed by gangsters), and Hall dedicates this sequel to his friend. I haven't read The Blind Spot, although I feel like I have since large sections of The Spot of Life involve characters finding bits and pieces of a manuscript (which is conveniently the earlier book) and reading them aloud.
The Spot of Life isn't great, but it is representative of a solid 1930s sci-fi serial with lots of action, a small amount of romance, and plenty of science.