Boundless Reader has two readers because comics and novels want different things from a page. The app picks the right one for what you opened. Everything else here, the taps, the auto-scroll, the resume behaviour, works the same in both.
Two readers, one set of gestures
The webtoon and comic reader scrolls in one continuous vertical strip, which is how manhwa is drawn to be read. Reach the end of a chapter and the next one continues in the same scroll, rather than dropping you back to a chapter list to start again.
The prose reader handles novels and other text. It adds two things worth knowing about: an in-content chapter title card, so the start of a chapter reads like the start of a chapter instead of sitting under a header bar, and a thin progress hairline under the header instead of a percentage.
Tap zones
Tap the left or right edge of the screen to jump a page or a screen in that direction. Tap the middle to toggle the reader chrome, the controls around your page.
It is the oldest interaction in comic readers, and it works because your thumb picks it up in about four taps. Each edge jump flashes red or green along the side you tapped. That tells you which way you just moved. On a long strip the panel either side of a jump can look nearly identical, so without that flash a jump reads as a dropped tap. Tap again without noticing it, and you have moved twice instead of once.
The edge zones are proportional but capped in absolute width, so they stay about a thumb's worth of screen even in a large iPad or Mac window, rather than ballooning into several hundred points.
Auto-scroll
Long vertical chapters want to scroll themselves. There is a play and pause button in the reader controls, and a speed you set to your own pace, since a dense prose chapter and a fast action sequence do not call for the same speed. Panels are not evenly sized, so any fixed speed is wrong somewhere. That is why the answer is hold to stop and not a second speed setting.
The part that matters day to day is hold to stop. Press and hold anywhere on the screen and the scroll halts for as long as you hold it, then picks up again when you let go. That is the natural reflex when something on the page needs a second look, and it works with the thumb that is already touching the glass. If you would rather scroll by hand, leave auto-scroll paused and it stays out of the way.
Picking up where you left off
Boundless tracks exactly where you stopped inside a chapter, instead of only the chapter number. Close the app mid-page and reopen the title later, and it puts you back at that exact point instead of at the top of the chapter.
That position lives locally on the device you were reading on, alongside the rest of your reading data. Signed out, it does not leave that device. Your library covers what is stored and where.
Moving between chapters
The chapter list opens from a title's detail screen and from the reader chrome itself. For working through a long backlog it also has multi-select: a Select and Cancel toggle, quick-select chips for All, None, Invert, and Unread, and a bulk action bar with Download, Read, and Unread. Your library has the full rundown.
Reading offline
Download a chapter and it reads exactly like an online one, with no connection required. Nothing is cached on a server anywhere, so downloads are the only offline story there is. Download chapters one at a time, or queue a batch from the bulk action bar before a flight or a dead spot.
How sources fit into the reader
The reader loads content directly from whatever site the source you installed targets. Boundless does not proxy or host any of it. So when a chapter will not load, the fault is usually the source's target site, not the reader.
Two things help when that happens. The in-app browser button on a title's detail screen opens the source site inside the app, so you can see exactly what it is returning instead of guessing. Removing a source and reinstalling it is harmless: your library, progress, and history are stored separately from the extension. Troubleshooting goes through specific failure cases.
On iPad and Mac
On a larger screen, long-form reading stays width-capped and centred instead of a line of prose stretching across a whole monitor. Past that one adjustment, the gestures, the auto-scroll, and the resume behaviour are the same as on the phone.
Where the tap zones came from
The reader used to have a much dumber problem than any of this: the tap layer sat underneath the chrome in the view hierarchy, so it quietly ate the taps meant for the close button while the chrome was showing, which is the only time you can see the close button. Fixing it was part of a round of work on how the reader feels to hold, which is where the flash feedback, the capped edge zones, hold to stop, and cross-chapter scrolling came from. The longer version is in Rebuilding the reader around the tap.
If none of this is open in front of you yet, start from Getting started. If the reader has nothing to show, Adding sources is the next stop.