Patricia Cornwell. Pick any title.
Maybe not the worst, but I remember reading a John Grisham novel about a decade ago, and I had liked everything before that, to varying degrees. I think it was “The Appeal”. I’ve since blocked out the plot and details. Anyway, we were on a road trip, it was all I had, and my disgust at the blatant political insinuations had been burgeoning for 400 miles. When I got to the last page, I chucked it out the window into a cornfield.
And then I forgot about it, and bought it again at a thrift shop a few years later…sigh
I do like me some Grisham when he’s talking about genteely redneck old-money dissolutes (Harry Rex, etc.).
This was one of my big problems with The DaVinci Code too. The protagonists manage to solve an anagram while running away from the police, but later when they’re sitting on a plane with nothing to do but focus on the next clue they’re stumped for way too long by a message that’s simply written backwards.
SPOILERS! Sheesh. 
This made me think about Frank Herbert’s work (numerous Dune sequels). The thing plays out like a “Lensman Arms race” (Lensman Arms Race - TV Tropes).
Everybody is smarter, faster, better than the last guy, but looks like a dumb schmuck compared with the next guy.
This is really exemplified in his book, “The Dosadi Experiment”. There, the really smart guy gets played by a smarter alien guy, lives briefly among the hyperacute Dosadi, first as a naif but soon rising to the top, then returns to make terribly smart alien look like chowderhead.
This happens when the writer is not as smart as the people he wants to write about. *
But thinking of the extended Dune series & Herbert reminded me of the recent Dune prequels (written by others). I could barely read the first one. Not one idea not already overworked in the original series, all the good previous ideas stuffed into the first of the new series- I haven’t even looked at the others
*BTW, this is why I like Larry Niven so much- I think he (mostly) takes a lot of time out to really think about what his smart guys are going to do/say/think. Sometimes it makes it read a little chess-y, but at least the smart guys aren’t asked to do stupid things to make someone else look smarter.
And you just described the show “Scorpion” to a T. People who are supposed to be geniuses doing idiotic things in the name of being geniuses - and that happens multiple times every 5 minutes.
One problem with the “everyone is smarter than the one before” concept is that the audience doesn’t get any smarter.
JAmes Patterson is the Edward Stratemeyer of the 21st Century.
the show “Scorpion” will go down in history as the greatest example of “Marty Stu” on TV. 
Had to look him up and yes indeed. These guys are more like word factories than authors.
Stephen King said something snarky along the lines of “Can Patterson write a 200 page book with 190 chapters? Yes, he can.” All that blank space makes it hard to read, content aside.
There was a long running joke (which Asimov cultivated, because he thought it was funny) that Asimov was a collective, or clones, or a hive mind, because, like, SF, and, that many books?
And somewhat off the subject, but the author is a self-centered, litigious curmudgeon. I have the misfortune of knowing him. he may be kind to puppies - people, not so much.