Apple released the first developer beta of iOS 13.4 a few days ago and Apple blogs were quick to share the usual in-depth deep dives into what changes it would bring. These changes are pretty small, but from what I can tell they've all missed some equally small changes to Apple Books also.
Here's a quick comparison between Apple Books in iOS 13.3 and iOS 13.4 developer beta 1:
Can you spot the differences? The chapter select button has moved from the top right, to the bottom right, the 'sleep timer' button is now a much more descriptive image, the playback speed indicator is larger and there's now an elipsis menu near the track name which opens the Sharesheet. The track scrubber and names have switched over as well.
Look, I did say the changes were tiny, but like I said I've not seen these particular tweaks mentioned anywhere so I couldn't resist my little exclusive of my own. The fact that I'm one of the only people I know that use Apple Books multiple hours a day, thus in a relatively rare position to notice such menial changes is by the by. I love the Apple Books app and, while these tiny changes make no difference to how I, or others, use the app, it is nice to see there is still a tiny focus on the app still from Apple's end.