Can I choose my own fonts and text size for the book's interior?

Yes. Open your book, find the "Book design" card on the right, and select "Custom" (the wide card at the bottom of the design list). A design studio opens where you choose: the font for chapter titles, the font for sub-headings inside chapters, and the font for paragraphs — from a curated list of book-quality serif, sans-serif and Chinese typefaces — plus the text size (9.5–14 pt), line spacing, an accent color (or monochrome), the chapter-opener style, first-line indents and drop caps. A live page preview shows exactly how your pages will look as you adjust. Your choices apply to every export format: PDF, EPUB, HTML and DOCX.