I prefer DSReader. It would be nice if it had more scrolling options than just "go to the next page" but it's still a good option, since it uses font files directly from your computer. Plus it's got several other font options including white-text-on-black-background and subpixel antialiasing to make books as readable as possible. Just make sure you create a "DSReader" folder on your card first. In my case, DSReader tried to make that folder itself and corrupted the whole card by mistake.