"Perhaps include more pictures, ask questions of your readers, provide a deeper insight into your topic (such as what this book is about)."
More pictures could be good in general, but maybe not in the case of books (for copyright reasons). Probably the front side and the back side of the book is okay, but other than that, I don't want to risk it.
Asking questions can be also a good idea, but I already wrote what this book is about. Not in this blog post, but in the blog post mentioned in this blog post.

"One trick that I occasionally use is to talk about a controversial topic. That get’s people talking."
I will think about it, but I think it's not good, if you have to talk about a controversial topic to get people talking. I rather like to talk about what I am doing, what I like and these are not controversial. But maybe I will try it.

"Also enter competitions. There’s some great writing competitions on Steemit. And by entering them your content is immediately put in front of a lot of people."
Competitions/challenges are also a good idea, I already tried some of them. Yesterday I made one for myself to be more consistent/active.

Thank you for taking the time to writing these suggestions!