How do you use your Android as an eBook reader?

If you don't use your Android as an e-reader, then what do you do when you're in line, or in a waiting room, or early for an engagement? Texting, Facebook, emails... sure, but when they're all taken care of, leaving only yourself as companion for 10 minutes, read a chapter of your book (unless you're reading Tolstoy, of course, whose chapters are books, and whose books are series). I even like to download a copy of books sitting on my nightstand, so I can continue the book I'm already reading (if they're public domain, that is).

Amazon Kindle and Google Play Books are top options, but I like backups, so I also have Sony Reader. I had Nook, but never found a book there that I couldn't find in Kindle (attempt 1) or Google Books (attempt 2). It's a decent selection, but Nook never really came through for me, as other options have, so I deemed it clutter.

Kindle recently released one of those updates you actually notice. Scrolling through the on-device library is now "carousel," like iTunes' Cover Flow (which was stripped from version 11; no, I didn't use it, but still... it looked cool). Changes to the store appear to be primarily cosmetic, but definitely an improvement. Overall the app looks more like Amazon's own Kindle devices. But the best change I've noticed is that now books I have finished, instead of maddeningly insisting I've read only 99%, agree that 100% has been read. See screenshot: I have closure.

Sony Reader was just added to the Play Store last month, so I haven't used it much yet. The only information I have about the selection here is from someone I know who owns a Sony e-reader, and is very happy with it.

Aldiko is the self-proclaimed "leading eBook application for the Android platform." The number of downloads is on par with Kindle, but Aldiko's statement that the app comes "pre-installed in 20+ different Smartphones and Tablets" makes me think the majority of those might be from overseas, interestingly; I don't know of any phones here on which it's pre-installed.

Which app you like the best really comes down to personal preference, but whichever you choose to use primarily, I recommend downloading a couple other top choices, so when you can't find a book on one, you'll have others to try.
Click for more information and downloads:

Amazon Kindle (I'm happy to inform you that their link to download works.)
Google Play Books (This one is pre-installed on many Androids.)
Barnes & Noble Nook (Their link works too, but took several seconds to find, which is mediocre.)
Sony Reader (I mention links, because their link does not work. On top of the outdated reference to the Android Market instead of the Play Store. Here's a link directly to the download.)
Aldiko Book Reader (This one made the cut because it's stupendously rated... nothing to do with the venerable icon. But beware: there's a run-on sentence right on the Aldiko homepage.)