I chuckled to myself at this bit because it's the type of productive-but-utlimately-unnecessary task I'd find myself doing if I were trying to write a book.
Not trying to be a downer, that's an impressive streak and I hope your book does well!
Yes, I have to work hard to limit my non-writing tinkering, so I timebox the design stuff pretty harshly.
I started the book four years ago, so the first design was unreadable on mobile devices (fixed position navigation will do that!). After a number of complaints, and the creation of Google Web Fonts, a mobile-friendly better design was a necessity.
I just finished another redesign that will launch when the last chapter is done. It's even more mobile friendly and has a front page that reflects the completed status of the book. It also just looks a hell of a lot better. :)
I chuckled to myself at this bit because it's the type of productive-but-utlimately-unnecessary task I'd find myself doing if I were trying to write a book.
Not trying to be a downer, that's an impressive streak and I hope your book does well!