I say this as a fan and user of Moon+ for several years, but HarryT's comment is spot-on, and is still correct. Moon+--and most Android reader apps in general--are indeed bad about giving you a simple working default style setting that gives you the option to use the publishers' CSS, unchanged.

In many, perhaps most ebooks I own, this is a non-issue and Moon+'s style changes are welcome, even preferable over the publisher styles. This is particularly the case with straightforward layouts, like novels, and the default styling changes by a lot of Android apps are sensible.

However there are a few books with complex layouts, for example drama involving complex character dialogs, or poetry with complex stanzas and indenting, that Moon+ just mangles and can not seem to get it right. But it's not that they 'can't do it, it's that they won't, for some inexplicable reason. Case in point, you can easily get a reader app that follows publisher CSS by default or at least lets you select that option--such as the built-in Calibre reader for PC. For Android, examples include the Google Play app, the Pocketbook app, and the Bookari app (another MR reader yesterday alerted me to the fact that Pocketbook and Bookari handle this issue well). Then you realize this shouldn't be that hard, and it's kind of mystifying as to why ALL reader apps don't give you a simple toggle "Display using all Publisher CSS settings."

Yes I know, as someone already said, Moon+ includes a "Show Preview with publisher formatting" toggle. And when you enable that, you get a view of the publisher's default layout. But that's only a preview. If you play with this for just a few minutes, you quickly learn that this "view" in Moon+ is crippled. A lot of the functionality that causes you to choose a reader app in the first place is not available, for instance, the only pagination option is scrolling, footnote links don't work, you can't add annotations, etc etc. It's a "preview" mode ONLY.

So yeah, it's kinda mystifying to me why these apps like Moon+ don't enable a fully functional view that uses all the Publisher CSS settings. With really complex layouts, this is about the only way to display the book's content cleanly unless you're prepared to do many hours of minutia hacking the CSS for a specific book just to get it to render correctly. As users, we shouldn't have to do that.