iReader

iReader is an app that gives you access to more than a million books and comics free of charge, with the ability to download them directly to your Android device. Plus, you can use the app to read any book or document you've downloaded previously.

When you first start using iReader you have to choose a genre that you find interesting so that the app can recommend books that you might like. You can also use the search function to quickly find any book that you might be looking for.

One important detail to note is that although the majority of the books available on iReader are free, there are also some paid titles. To download those books, you will need to buy them first. Fortunately, you can buy them using money that you earn within the app itself, so you don't need to spend real money.

iReader is an excellent app for avid readers that lets you not only open and read your books and PDF documents, but also download and enjoy thousands of free books and comics. On top of that, you can change the size of the font, customize the margins, etc.