"Meditating" is a broad term encompassing all of my spiritual practice - the "active" part of my engagement with questions of truth and meaning.
I have read and benefitted greatly from the following works on meditation, mindfulness and buddhist thought:
"Zen mind, beginner's mind" by Shunryu Suzuki
"The wisdom of no escape" by Pema Chödrön
"A Path with Heart" by Jack Kornfield
"In this very life" by Mahasi Sayadaw
the podcast "Insight Hour" with Joseph Goldstein
For converging thoughts on Catholic contemplation and ethics, I cannot recommend highly enough
"Gravity and grace" by Simone Weil
If one is interested in these topics, maybe also philosophy of science, and prefers reading fiction, there's
"Zen and the art of motorcycle maintenance" by Robert Pirsig
"Lila" by Robert Pirsig
"Siddharta" by Hermann Hesse
If one is interested in these topics, or just appreciates nature, and likes poetry, you can hardly go wrong with
"Devotions" by Mary Oliver