“Readability assessment for book-level long text is widely needed in real educational applica-tions. However, most of the current researches focus on passage-level readability assessmentand little work has been done to process ultra-long texts. In order to process the long sequenceof book texts better and to enhance pretrained models with difficulty knowledge, we propose anovel model DSDR, difficulty-aware segment pre-training and difficulty multi-view representa-tion. Specifically, we split all books into multiple fixed-length segments and employ unsuper-vised clustering to obtain difficulty-aware segments, which are used to re-train the pretrainedmodel to learn difficulty knowledge. Accordingly, a long text is represented by averaging mul-tiple vectors of segments with varying difficulty levels. We construct a new dataset of GradedChildren’s Books to evaluate model performance. Our proposed model achieves promising re-sults, outperforming both the traditional SVM classifier and several popular pretrained models.In addition, our work establishes a new prototype for book-level readability assessment, whichprovides an important benchmark for related research in future work.”