Georgia O'Keeffe in the West . Collects many of her later paintings especially those of SW landscapes and Indian artifacts. Cowart, Jack, Juan Hamilton, and Sarah Greenough. Catalogue from one of the definitive retrospective exhibits. Probably best collection of her work.
Good intro essays plus reprints of lots of letters.
Goodrich, Lloyd, and Doris Bry. Georgia O'Keeffe . Catalogue from one of the first major retrospectives. Yale U P, 1993. Catalogue from recent international retrospective exhibit which emphasized OK's abstractions.