Focusing on what authors can do to facilitate learning from content area textbooks, this report labels authors as "considerate," providing text that readers can understand with a minimum of cognitive effort, or as "inconsiderate," creating text that requires a conscientious, highly skilled effort if readers are to comprehend it. The discussion is organized around four text characteristics: structure, coherence, unity, and audience appropriateness. These characteristics are defined, illustrated, and related to research on their effect on comprehension and learning. Also included is a set of guidelines and a checklist for editors and authors of textbooks and for people who select and evaluate textbooks. (AEA)