I'm answering out of general knowledge of application development, not any particular knowledge of book app creation.
There are probably tools designed specifically for what you have in mind. I don't know, and you should continue looking into that.
However depending on what you expect your book to do, you may have a variety of options available.
You mention converting HTML. If your book already is, or could be, implemented as a web page, you could display that exactly as-is on a mobile device. The "app" would merely be a launcher to display local content in the device's web browser.
This is a popular method of cross-platform development for many kinds of apps, and there are many tools to make the app package.
Another option, if the interaction in your book is simple animation, transitions and sounds, you could do do all the design and element production, and hand the pieces over to just about any mobile app developer, even someone just learning. Stringing pieces like that together is a pretty trivial app, when the design and graphics are already done.
ApK
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