I read only recently that a countervailing view was that the British and Canadian left pinned the bulk of the German Army allowing the American breakout to close the Falaise Pocket.
That was always Monty's plan which had been agreed to by Eisenhower. The Brits and Canadians were the numerically dominant force at the start of D-Day and took on the strongest German formations around Caen. The Americans had to build their forces up and by the time of Operation Cobra were the largest force. Post war when the memoirs were published was when the Americans disparaged Monty's plan. It didn't help that Monty had annoyed everyone with his personality. His press conference after the Battle of the Bulge was his personal "bridge too far" as far as the Americans were concerned.
As for Arnhem Monty, had always argued for the strong single thrust to break into Germany and the Market-Garden plan was the result. Once again a plan that was approved by Eisenhower. What is fascinating about the battle are the number of what ifs that could have made it successful. One aspect often overlooked is the American's 82nd Airborne failure to take the Nijmegen bridge when they could have instead of focusing on the Groesbeck Heights.
Anyway Anton Beevor is a very readable author of history. Another author is James Holland, who also is not a big fan of Montgomery.