Aldiko is probably the second best Ebook reader on the market, the first being Kindle. But Kindle is just really famous and polished, it's not necessarily the single most diverse, option savvy E-book reader on Android, and neither is Alkido, but it looks just as good as Kindle and has a lot more functions available.
First of all you have a huge library to choose from, free E-books, paid E-books, your own E-books -- as long as they make an appearance dressed up as Epubs, TXT's, HTML'S, a Word document, PDB's and PDF's. Adobe DRM technology is also supported, so you can read all those pesky books from Adobe that only work in your Firefox browser courtesy of a plug-in.
You can change from day to night view and all of your books are tagged and search ready, even the ones you've imported. You can have fun with adjustments to text sizes, font types, font colors, and background colors, even margins and alignment are customizable. Plus you can bookmark various pages, adjust the brightness easily and your last page is saved if you exit the app rather suddenly.