John Donne wrote some of the most beautiful, intelligent, and passionate poetry in the English language! With some poets you get 1 or 2 of these qualities: with Donne you get all 3, and so I highly recommend his poetry to all lovers of poetry and English literature. The language is archaic and at times difficult, but that's also some of its beauty and charm. What's more noteworthy but less noticed than the oldness of the language is how fresh and alive it still seems and must have seemed in centuries past! While I love Donne's poetry especially because of his intelligent and beautiful passion for God, even those without religious faith will appreciate the brilliance and glory of Donne's poetry.
If you're able to keep up with Donne's poetry, you'll discover startling phrases and juxtapositions which were frowned upon in ages past but which I find helps invigorate the modern reader. Whether your primary way of apprehending poetry is religious, intellectual, or aesthetic, Donne will be a delight to you as it does me. Donne's poetry also has a very personal association with me: when I was courting my wife and in the early years of my marriage, I would read her the poetry of Donne and George Herbert. She not only loved the poetry but loved me more for having read it to her!
This Wordsworth Poetry Library edition contains the complete poems of Donne (some editions don't), as well as an introduction, chronology, notes, and bibliography.
Highly recommended!