Public Domain. Those that are in the public domain have links to where you can actually read them online.
One link I have is only to another post about a book I checked out at the library. That book is The South Side: The Racial Transformation of an American Neighborhood by Louis Rosen.
Anyway I just wish there was a way to create an app where you can access those readings. Therefore it's possible to be able to read these works which mainly would include two books by economist Adam Smith, Second Treatise of Government by John Locke, On Liberty by John Stuart Mill, The Social Contract by Jean-Jacques Rousseau, Democracy in America by Alexis De Tocqueville, Narrative of the Life of Frederick Douglas: An American Slave by Frederick Douglass, and finally Up from Slavery by Booker T. Washington. So these books involve some Black history, political philosophy, even classical economics.
This would make getting an iPad or similar device much more worthwhile! :P