There are options though.
Fortunately, there are free eBooks out there, but they are often hard to find.
Here are a few great options for starting off your library without spending a dime.
Amazingly, many of them are quite good.
Google Books
Google Books is perhaps the biggest source for free eBooks.
All available on their website in epub and Kindle format.
Barnes & Noble
Barnes & Noble has a section for free eBooks.
They are at least good for testing the functionality of your unit.
Planet eBook
This is the option I prefer.
They even have 1 page or 2 page format options in each file.
Get great books like Frankenstein, Les Miserables and 1984 for free.
Thanks to Xseraph for recommending this one.