From what I understand, the current darling theory for the collapse of the Aegean Bronze Age (includes Greece, Hittites, and even Egypt was threatened) is called "Systems Collapse," where the interrelated economies and societies of the eastern Mediterranean allowed for widespread disruption throughout the region: as one culture hit a speedbump (pirates, Sea Peoples, famine, earthquake, etc.) the others were impacted as trade slacked off and their own problems intensified. It's a combination-of-factors theory, and it's the one I find most convincing.
The Dorians is what the ancient Greeks themselves believed caused the destruction of the Mycenaean palaces, but archaeology seems to indicate that the Dorians moved gradually into the vacuum left by Mycenaean collapse. Like the Mycenaeans (proven by Linear B decipherment in the 1950s), they were Greek speakers and their arrival didn't seem to bring the widespread destruction to the region. The Sea-Peoples theory has been off and on, but I believe it's accepted as the catalyst for the collapse of the Hittites, and their attack on Egypt is documented in Egyptian records. (some of these Sea-peoples, the Paleset - ended up as the Bible's Philistines).
Here's a pretty good list and description of the historiography on the subject, including the various theories and the authors who argued for them:
http://projectsx.dartmouth.edu/class...les/28.html#18
As for the Dark Ages, more and more is coming to light via archaeology. The best books I know are C. Thomas'
From Citadel to City State and Langdon's
New Light on a Dark Age (available
used at Amazon.com
in paperback for the bargain price of $995.00 + shipping:
http://www.amazon.com/gp/offer-listi...557063&sr=1-11)
Couldn't I at least get a hardcover for my $1000?