When literacy instruction uses books selected on the basis of thematic content, it can foster the attainment of literacy goals while developing readers' knowledge. This paper provides a rationale for the use of thematically-related texts in literacy instruction and describes some thematic units that have been a part of literacy intervention research with struggling readers. Examples illustrate how to begin with simple texts, read multiple texts on a topic to develop knowledge, include a more challenging, culminating text, and use themes to develop useful genre knowledge. Tips for teachers who wish to develop their own content themes are suggested.