Jack Reacher thrillers.
They are pure fluff, but extremely well crafted, as evidenced by the fact that serious writers are fans.
https://www.theguardian.com/books/2019/oct/18/fearless-free-and-feminist-the-enduring-appeal-of-jack-reacher-
"For stories to be as successful as these, they need to be read by people who don’t generally read. But what makes Reacher so fascinating is the books’ appeal not only outside, but within the rarefied circles of the literati – unlike, say, the work of Dan Brown or EL James. Their success with the grandes dames of literature is especially striking. Antonia Fraser is a fan. Kate Atkinson is a fan. Margaret Drabble, asked earlier this year by the Guardian what book she wished she’d written, answered: “Anything by Lee Child. What page turners, what prose, what landscapes, what motorways and motels, what mythic dimensions! I read, awestruck, waiting impatiently for the next.”"