I know that The Big Four is considered one of Agatha Christie's weaker books (including by Christie herself), but I actually kind of enjoyed it? In part, it probably helped that I read it via Serial Reader, which matched well with the episodic feeling in the book. It also helps that it's quite short, and each episode is partly self-contained, meaning there's not so much time to get overcomplicated and build up a huge catch of the proverbial fishies.

It's of course melodramatic and over the top, with a bit of the flavour of Sherlock Holmes vs Moriarty, but I just kinda leaned into that and let it go. Hastings wasn't as unbearable as usual (though I still don't like him)... though I found Poirot pretty insufferable, especially with his repeated decision to let Hastings suffer in ignorance because he can't act. 

I'm still not a Christie fan, but this one worked surprisingly well for me.