Besides having a ton of customization available for fonts, font and paragraph spacing, margins and more, it also tracks reading statistics for things like length of time read, pages read, reading speed in WPM (estimated), and so on. Moon+ Reader is a fantastic reading app for Android. Big/small text, dark/light background, whatever. The nice thing about ebooks is that you can make the appearance whatever you want. My ebook app is Moon+ Reader, and I prefer white text on a black background. I have had friends try to loan me a physical book, and I'll just buy the ebook. While many people talk about the experience of physical books, I personally now find ebooks a much more enjoyable experience. I started reading ebooks because I was on the road for work, and ebooks were far more portable when you're a fast reader.

I upgraded to just using my small, cheap smartphone (one handed reading is awesome). Spend some spare time reading Sherlock Holmes instead of Facebook when you're out and about. There's absolutely no reason not to have an ebook app on your phone and download some free books from Project Gutenberg. You don't have to choose one or the other. One thing to remember is that it's entirely possible to do BOTH physical books and ebooks. I just bought it today with my Google Opinion Rewards credit. It adds a few features like TTS, sync, and more customization. The Pro version is half-off (US$2.49) through the end of August. It's not even as much advertising as a Kindle with Special Offers. You never see an ad when opening the app or while reading, unless you accidentally bump the back button. The free version has ads, but they are super unobtrusive - only at the bottom of the library screen and sometimes when switching from the book to the library. There is plenty of layout and font customization. You can also use the volume keys to turn pages, which is great if you read while wearing gloves. You can set it up so you can read page by page or by scrolling - or both at once. It has a night mode that is easy to toggle, though not automatic (unless that is a pro feature).

(I've never tried the PDF viewer, though.) It's very lightweight, and always perfectly remembers your reading position. It's a great eBook reader, supporting EPUB, MOBI, and PDF, as well as other formats.

Ivona reader spare copy