Prof. Kieran Healy (Sociology, Yale University) shares some nice insight into the process of writing a book in Quarto using R in this post. The output screenshots he shares look beautiful, and the idea of deploying the same content as a clean PDF and a responsive website is awesome. A full draft of the book, Data Visualization: A Practical Introduction (Second Edition), is available as a website here.
I have grown increasingly tired of writing in any format other than a plain text file I can easily version control and move around, so the idea of writing a book in Quarto is appealing to me (as long as it has enough technical content to justify the format).