I've noticed lots of folks point to 'New and Selected Poems, Volume One' as the entry point, and honestly, that's the safe recommendation for good reason. It gives you a broad sweep of her earlier work, so you can see what resonates without committing to a single themed collection. 'Why I Wake Early' was my first, though—its focus on morning light and those small, daily acts of attention felt less intimidating somehow, more like a gentle guide than a grand statement. I'd say grab whichever one you find at the library first; the gateway isn't a specific book, it's any page where her wonder clicks for you.
Her poems operate at this very specific, attentive frequency. If you're coming from flashier or more narrative poetry, her quietness might feel flat at first. I had to learn to slow down to her pace, to see the observation as the event. Starting with a 'Selected' volume helps because if one poem doesn't land, the next one might.