School textbooks are commonly criticized. This article reviews research in revising instructional text by examining multidisciplinary research in readability, text structure, text interestingness, expert revisers' strategies, and readers' comprehension strategies. Findings are that much of this research is limited by a simplistic view of reading, the use of experimentally contrived texts and contexts, and a dependency on recall as a measure of comprehension. A promising line of recent research uses readers' verbal protocols to guide revision and develop revision principles. Further research needs to: (a) develop other innovative ways of measuring comprehension, (b) focus on subject specific concerns, and (c) examine classroom contexts of textbook use.