Ward, S. A., and R. H. Jr. Halstead. Computation Structures. Cambridge, MA: MIT Press and McGraw-Hill, 1989. ISBN: 9780262231398. [6.004 text]
Agarwal, Anant, and Jeffrey H. Lang. 6.002 Notes: Foundations of Analog and Digital Electronic Circuits. San Francisco, CA: Morgan Kaufmann/Elsevier, 2005. ISBN: 9781558607354.
Boolean Algebra: There are many excellent descriptions of Boolean Algebra at various technical levels on the Web. You can find many through Google.
Truxal, John G. The Age of Electronic Messages. Cambridge, MA: MIT Press, 1990. ISBN: 9780262701020. Lots of examples of codes, at an introductory level.