In this paper I discuss how taking a particular literary theory--the implied reader--serves to offer a focus for the teacher's initial reading of a text and provides a formative assessment tool. Iser's Implied Reader theory is discussed, after which a picture book, "Where the Forest Meets the Sea" by Jeannie Baker, is analysed from this perspective. An account of a series of reading events with Year 4 children then follows. An analysis of these readings highlights where the pupils were able to take up the invitation offered by the text and where there were difficulties. Finally, implications for teachers' subject knowledge are discussed.