The liberty fund publishes excellent classic works of history, economics, law and political science very inexpensively. Usually library grade hard cover and soft cover books.
They have put virtually their entire library online for free in pdf and sometimes html format.
I especially like the pdf files for convenient searching when doing research. You can find their library of economics here, but keep in mind it's not only economics - actually that's the minority. However it seems like the online library of liberty may be more accessible in for the same material.
Here's a list of their authors, many are historical giants and nobel prize winners:
B Baden, John Bagehot, Walter Barbon, Nicholas Barry, Norman Bastable, Charles F. Bastiat, Frédéric Bentham, Jeremy Böhm-Bawerk, Eugen von Brennan, Geoffrey Brough, William Brown, Pamela J. Buchanan, James M. Burke, Edmund
C Cairnes, John Elliot Cannan, Edwin Cantillon, Richard Clark, John Bates Coase, Ronald H. Cobden, Richard
D Dolan, Edwin G.
F Fetter, Frank A. Fisher, Irving
G George, Henry Gray, John N.
H Hayek, Friedrich A. Heckscher, Eli F. Henderson, David R. Higgs, Henry Hirst, Francis W. Hobson, John A. Hodgskin, Thomas Hollander, Samuel Hoxie, Robert F. Hume, David
J Jasay, Anthony de Jevons, William Stanley
K Keynes, John M. Kirzner, Israel M. Knight, Frank H.
L Lachmann, Ludwig M. Lalor, John J. Laughlin, J. Laurence Leggett, William List, Friedrich
M Macaulay, Lord (Thomas Babington) Mackay, Charles Mackay, Thomas Malthus, Thomas Robert Marcet, Jane Haldimand Marshall, Alfred Marx, Karl Mill, James Mill, John Stuart Milton, John Mises, Ludwig von Molinari, Gustave de Moss, Laurence S.
N Newcomb, Simon North, Sir Dudley
O O'Driscoll, Gerald P., Jr.
P Paul, Ellen Frankel Pigou, Arthur, C.
R Rae, John Read, Leonard E. Ricardo, David Richter, Eugene Robbins, Lionel Rogge, Benjamin A. Rothbard, Murray N.
S Say, Jean-Baptiste Senior, Nassau W. Shaw, George Bernard Smiles, Samuel Smith, Adam Smith, Bruce Smith, Vera C. Spencer, Herbert Stroup, Richard
T Taussig, Frank William Taylor, John Thirlby, George F. Tracy, Antoine Louis Claude Destutt de Tullock, Gordon Turgot, Anne Robert Jacques
V Viner, Jacob
W Wagner, Richard E. Walker, Francis A. Whately, Richard Wicksell, Knut Wicksteed, Philip H. Y Young, Arthur
For several of the authors, they have published their entire life works.
This is incredibly good stuff if you're intersted in these areas.
Have a wonderful day,