If your phone can run Java applications, you can put free books on it, easily. I've been using the free books found at
Books in my Phone for some months now, and I'm a huge fan.
What they've done is take mostly old out-of-copyright books, along with some new ones by Creative Commons fans like Cory Doctorow, and compiled them into JAR files. They've got some kind of book reader application, and all that they change for it is the text file that makes up the content.
The file sizes are really small, so the fact that the reader code is repeated doesn't matter. I've got eight books on my phone right now, and the size is negligible compared to my MP3 files and photos.
I read
Someone Comes to Town, Someone Leaves Town this way, and really enjoyed it. I'm currently enjoying
Dogland by Will Shetterly. These are both recent books, but I also got a big kick out of
Seventeen by Booth Tarkington, which was published in 1914.
You might have to experiment a little to figure out which of the available formats works on your phone and where to find them on your phone's menu. My phone has a cable for interacting with the computer as a USB drive, which lets me quickly put files on the memory card; I made a Books folder on the card. Then I find then find them via the Games & Apps>Memory Card> menu option, which lists the folders on the card. You just have to figure out how you view the contents of your memory card on your phone.
Once you figure this out, though, you're on your way. And you can skip this process if you have a data plan and want to download books directly to your phone from the Books in my Phone website.
It's even possible to compile your own reader to take any text file you've got and convert it to something readable on your phone, but I haven't experimented with that yet. I've got to reread Pride and Prejudice and maybe take a shot at Middlemarch or War and Peace first. Ooh, and I downloaded a collection of Chekov stories.
My mom would definitely approve.