This article presents 34 characteristics of texts and tasks ("text features") that can make continuous (prose), noncontinuous (document), and quantitative texts easier or more difficult for adolescents and adults to comprehend and use. The text features were identified by examining the assessment tasks and associated texts in the national assessments of adult literacy administered by the U.S. Department of Education, as well as existing research in literacy, linguistics, reading, and mathematics. The contribution of the proposed text features to the overall ease or difficulty of literacy tasks has been largely validated through psychometric analyses. The article explains how knowledge of text features might enhance teacher preparation, professional development, and text selection or creation. (Contains 3 tables and 3 figures.)