I think there's something to be said for that approach, and I'd probably go for that approach, at least some of the time, if there were a way to keep the devices "on the same page," as it were. I don't really want to keep multiple
books going at the same time, I've done it before, I just prefer not to, so I'd need a way to keep the same book at the same place (or pretty close) on multiple devices. Of course, that also drags in the format and DRM issues.