I did a search and came across a Wikipedia article on comparing iOS book readers. There are a lot more than I thought! The one that caught my eye was Marvin. Location syncing with Dropbox, using Calibre as a book manager (which I do anyway), Collections, annotations, themes, paragraph spacing (why is this omitted from so many readers?), swipe-brightness control, swipe-temperature control, and a whole lot more. You can even edit all the metadata and sync this back to Calibre. Including book covers.
It has more. A “Deep View” action will intelligently scan your book and extract names, places, and so on and generate an index on the fly. It will store words you look up in the dictionary so you build a vocabulary list. Custom actions (at least on the iPad) that look like you can leverage URL schemes to link into many other apps and web sites (e.g. search for images), downloading from OPDS servers (Calibre has one, but there are also others where you can download non-DRM books straight off the Internet)… and oh so much more.
Evidently I’m very impressed.
It’s not the ultimate reader for me yet, though. It doesn’t look like the annotations sync automatically like Google Play Books does, but there are two manual ways to do it, one is to run the backup task (which backs up books as well as annotations and bookmarks) or exporting the annotations via email. The latter seems better suited for transferring from device to device, since one click will import them again. It also only handles non-DRM ePubs, but I have already decided that is my go-to format, and Calibre takes care of any unencumbering and conversion tasks nicely.
I would like to see wireless connectivity to Calibre, and not just hardwired/USB connections supported.
I would ultimately like to see a reader that will index/search across my entire library (for reference books) but I think that’s possibly too ambitious at this point. The best I can hope for is that DEVONThink To Go will improve to provide an archiving and searching alternative/companion for ePubs, as well as PDFs.
It’s $3, or less than half the price of a cheap eBook.