I recently finished The Only Thing to Fear, by C. J. Henderson, writing under the pseudonym Robert Morgan. This is one of his Teddy London series. I didn't realize that it was actually one of the later ones when I bought it, as I haven't read the earlier installments, just a few London stories in anthologies.
I'll be blunt: it wasn't awful, but I didn't much care for it.
These days this book would be filed under urban fantasy. I'm not entirely sure this fits within the Cthulhu Mythos by my definition, but I figured it's close enough. Other Teddy London stories have featured Mythos elements, so by the infectious reference model this fits. And a monster called (spoiler) Q'talu does show up at the end, who I think is supposed to be Cthulhu with the serial numbers filed off, though given it talks to the protagonists that's not necessarily a safe assumption.
Detective Teddy London is Henderson's version of Brian Lumley's Titus Crow or August Derleth's Prof. Laban Shrewsbury, though fortunately rather more human. London is working in a Tibetan monastery, apparently as a result of something that happened in a previous book I haven't read. On the instruction of the abbot, he heads north into China, where he runs into the ghost of a silent ancient Chinese warrior and a stereotypical Mystical Old Guy (Irritating Subtype). He then bums around China for 170 pages. Meanwhile, his partners at his detective agency, including his fiancee, are getting worried because Teddy hasn't bothered to call them for months, and a meteor is about to smash into Earth. Most of this section frankly reads like Henderson took a vacation in China and was wringing every drop of local color from it he could get - for example, there's a chapter where London and Mystical Old Guy work on a tea farm for a few months while waiting for something to happen. (And of course London is better at drying tea then everyone else, I mean obviously.) Of course, eventually all this comes together in the Big Climax.
When Henderson finally gets to the action, it's okay, nothing special. But even then, his characters are mostly pretty flat, his plots uninspired and workmanlike, and his writing adequate. 2/5 stars.