evelyninthegarden said:The Gardener's Iris Book by William Shear
Shear's is my go-to book for information on iris care. I find it comprehensive, always helpful, and a delight to read.
For reading about and ogling pictures of cultivars, I have enjoyed:
A Guide to Bearded Irises: Cultivating the Rainbow for Beginners and Enthusiasts by Kelly D. Norris
Beardless Irises: A Plant for Every Garden Situation by Kevin C. Vaughn