Oh this is such a hard question. I tend to know my tastes very well and can figure out if a book is for me within the first 2 chapters. Are you able to clock that early on and put the book down or do you feel like you have to persevere once you've started? If so, I would recommend being harsh and just closing anything that isn't fully grabbing you after the first few chapters.

Another thing I like to do is research the favorite books/authors of authors I really like. Chances are you'll have somewhat similar taste to them.

When I get into a rut, I like to take a break from reading and busy myself with other things. With time you'll definitely find your way back to more fulfilling stuff! Also if you really feel like reading I second gene's comment, revisiting an old book or reading something you normally would never consider reading is a good idea too. I read some Agatha Christie for the first time last year when I was in a rut and didn't love it, but it was still an enjoyable experience reading something so different.

I hit streaks like this sometimes. I'll usually try to be a little less ambitious for a while, and return to a book or author I liked when I was younger, and wonder at what qualities lie in their writing that still grab me. Or I wonder if the answer is to release yourself from your own taste entirely; what if you tried reading a book or two really out of left field, sourced from some trustworthy randoms?

Best of luck.