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There is no good evidence as of now whether Agamemnon was a real person or not. It's possible that his name existed and was later attached to the leader of the Greek army at Troy, but this is all just conjecture. There have been some promising finds in the past century that lends itself to that idea, chiefly the Pylos tablets, among which the names Orestes, Atreus, Tantalus, and Thyestes all occur. There was also an Attarissyas who was "trouble" to the Hittites, and some have posited that that was Agamemnon, though it's mere speculation and, in fact, unlikely to be the case.
For an older but still solid introduction, check out Webster's 1958 monograph From Mycenae to Homer. You can find the reprint on Google Books.
I don't know what your access to scholarship is like, but a number of interesting papers that came out of an AIA session in 1981 published in AJA 87.2 (1983). You can also check out Snodgrass' Archaeology and the Emergence of Greece, which has some updated sections to point you towards more recent literature. For a more pop account, check out Eric Cline's Trojan War: Very Short Introduction.