Standards for literacy in the twenty-first century raise the bar on the complexity of texts and the tasks for which they are used. The strengths and limitations of contemporary approaches to text complexity are discussed with respect to major points raised in the six articles in this special issue. In addition, four features of text that are of central importance for reading to learn disciplinary content are discussed: topic complexity, genre and function, word-level indicators, and task complexity. We argue that if we are to ascertain sources of complexity and challenge when readers engage with text for purposes of accomplishing interpretive and explanatory levels of understanding, we will need to take into account text, task, and reader situated in sociocultural contexts of schools and communities.