The Battle of Normandy 1944

What happened to the Allied armies in Normandy in the months after D-Day, 1944? Why, after the initial success of the landings, did their advance stall a few miles inland from the beaches? Why did the British take so long to capture Caen? Why did the US infantry struggle so much in the bocage south of Omaha beach? Who was right about the conduct of the land campaign - Eisenhower or Montgomery? How did the Germans, deprived of air support, manage to hold off such a massive Allied force for more than 2 months? And if Enigma was allowing the Allies to read German battleplans, why did things go wrong as often as they did?