In addition to Wallace's recommendation, Elliott himself wrote two books: The Wave Principle and The Nature's Law. He also wrote some articles on Financial World, but the books will do just fine, though.
His "successor", A. Hamilton Bolton also wrote a lot of materials on the subject, and they were compiled together in "The Writings of Hamilton Bolton", which includes Elliott Wave Principle - A Critical Appraisal.
Other sources should be those who use EW. gharghur has a thread on EW, as well as quintrix. Wallace also, IMHO, has a good knowledge on the subject. Surely, there are plenty of others out there. An analyst at Alpari's forum also provides free analysis on currencies which uses EW.
After knowing the principle (which is actually simple), the major difficulty is to dissect the market movements into waves with satisfying accuracy. The latter obviously will require plenty of practices and patience, of course.
Good luck!
