There is a large amount of free literature out there, some legal, some questionable, but most of it can't be read on the iPad without being converted, and even then... I had a large selection of books that I had converted to read on my iPad, and then an update made the iPad decide it didn't want to read epub format anymore.
Needless to say, since I was done reading most of the files, I didn't bother re-converting and trying to read in PDF in iBook... Then I found the stanza app. Other than just NOT being able to figure out how to change books, its pretty cool. You can zoom in and out by pinching, if you save the zoom level it applies it to the entire book so you can go grandma and read with 30 pt font, or exercise your eyes and read it at 6pt... the illumination level is cute, you swipe up or down to increase or decrease the backlight. It also has a questionable bookmark feature, which I haven't figured out a use for... maybe it was for when the app wouldn't continue running in the background? Bascially you "fold" the top right corner to remember your place, again cute.
Over all, the app is good with the exception of not knowing how to close the book and go to another. I had to settle for learning how to crash the app at will, you zoom, cancel, and change the luminosity while the system is resetting the page and it crashes...>.> don't fix it, I can't close the book without that bug!
Update: The latest release removed the bug that crashed the app! Luckily before that I figured out that if you single tap in the middle third of the screen a plethora of options open to you, allowing you to close the book, jump between chapters etc etc. It has all the features and functions of iBook without any of the annoying limitations.
