Great topic! I think poetry is a big section of my antilibrary as well. I really enjoy creative, beautiful language, and exploring what can be done with it, but I don’t always read poetry all that often.
I think I do engage with language in a variety of ways, so I have a few recommendations, some that aren’t exactly poetry books proper, but relevant I think to the broader goal of engaging with poetry!
I’m a huge fan of hip-hop, and enjoy both listening and writing. I haven’t found many great books on hip-hop poetics (Book of Rhymes is an okay intro but super basic) but I always recommend e.g. just listening closely to great lyricists like Kendrick Lamar. If you’re into hip-hop you may find this book interesting; an anthology of poetry sort of aligned / inspired by hip-hop culture: The Breakbeat Poets
I really liked this one, about how metrical verse works. First half discusses the rules / how this kind of poetry works; second half is a great anthology of examples: Rules for the Dance: A Handbook for Writing and Reading Metrical Verse
This is one of my all time favorite books; it uses a lens of looking at a dazzling variety of different translations of one particular poem to explore all kinds of interesting topics around language and translation: Le Ton beau de Marot: In Praise of the Music of Language
Much shorter but similarly using translation / close reading as a lens for exploring poetry, is: 19 Ways of Looking at Wang Wei, With More Ways
For books with really great poetic language, borderline prose poetry, a few favorites are: Pilgrim at Tinker Creek, Invisible Cities, and Time and the Art of Living
I also love playful experimentation with language and constraints. One literary movement that exemplifies this spirit is the Oulipo. This is a good anthology / introduction to their work: Oulipo: A Primer of Potential Literature
And some really cool specific books that came out of this kind of Oulipean experimentation, playing with language in interesting ways: Eunoia and Exercises in Style