This study was undertaken to design, evaluate and refine an eBook-feature that supports students' decoding of unfamiliar text. The feature supports students' independent reading of eBooks with text-to-speech, graded support in the form of syllabification and rhyme analogy, and by dividing the word material into different categories based on the frequency and regularity of the word or its constituent parts. The eBook-feature is based on connectionist models of reading and reading acquisition and the theory of scaffolding. Students are supported in mapping between spelling and sound, in identifying the relevant spelling patterns and in generalizing, in order to strengthen their decoding skills. The prototype was evaluated with Danish students in the second grade to see how and under what circumstances students can use the feature in ways that strengthen their decoding skills and support them in reading unfamiliar text. It was found that most students could interact with the eBook-material in ways that the envisioned learning trajectory in the study predicts are beneficial in strengthening their decoding skills. The study contributes with both principles for designing digital learning material with supportive features for decoding unfamiliar text and with a concrete proposal for a design. The perspectives for making reading acquisition more differentiated and meaningful for second graders in languages with irregular spelling are discussed.