What do you wish you knew before launching your e-book?

Hell product hunt! I'm launching an e-book soon and want to utilize this amazing community to make it as successful as I can! For those of you who have been involved with an e-book launch before, what do you guys wish that you would have known before you launched your book? Marketing, platforms, content etc. Also, one unique challenge with ours is that we want to have sections where people write out some reflections. What's the cleanest way that we can format that into our book? Ideally, people would be able to type right into the book. Appreciate all the help we can get!