Robert Waldron, Walking with Thomas Merton: Discovering his Poetry, Essays, and Journals.
I'm getting ready to give a short talk about Merton's poetry, for a Lenten series at my church. Naturally, in addition to rereading Merton's poetry like a dervish, I'm reading others' writings about Merton's poetry, too. This is quite a new little book that details Waldron's efforts to get ready to give a day-long retreat based on Merton's poetry. Hence me picking it up.
Waldron's book is a journal he kept while preparing for the retreat. There are some lovely, well-considered and argued ideas; there's more uninteresting gobblety-gook. But the whole book's only 106 pages, so the skippable bits won't wear on you too much.
If you're interested in the poetry--and you've read it--you might enjoy this book, as an example of how someone else approaches teaching it. If not, or if that idea doesn't interest you, don't worry yourself. Go read the journals (again). They're so much fun. And even if it does interest you, you're better off with the more academic & much better written Heretic Blood: The Spiritual Geography of Thomas Merton, by Michael Higgins.