Final answer:
Book designers must consider the visual style, margin space, and feature boxes when preparing a book.
Step-by-step explanation:
When preparing a book, book designers must consider several features to ensure a quality reading experience. One important feature is the visual style, including font, colors, backgrounds, and overall design consistency. Another feature to consider is the use of margin space for notes, citations, figures, tables, and captions to prevent interruptions in the primary text flow. Additionally, book designers should think about incorporating feature boxes within each chapter, which provide additional documents, images, and resources for further exploration.