I would recommend the Little, Brown Handbook for studying grammar, and studying standard style guides instead. The Associated Press Stylebook (APS), the Modern Language Association's Handbook (MLA), and the Chicago Manual of Style (CMOS) are the top three. For ESL learnings, I'd recommend the MLA to begin with. I'd also recommend they invest in a Merriam-Webster's Dictionary and Merriam-Webster's Thesaurus (both are free online these days) — they could learn a lot just reading the thesaurus.

They cannot learn from AI what that grammar textbook and those style manuals can teach them.

I keep a Roget Thesaurus and Webster's Dictionary on my desk next to my computer. I enjoy thumbing through the thesaurus. And, I love learning new-to-me words.