Colossal Cracks: Montgomery's 21st Army Group in Northwest Europe, 1944-45 (Stackpole Military History): Montgomery's 21st Army Group in Northwest Europe, 1944-45 (Stackpole Military History) (Paperback)
By Stephen A. Hart (Stackpole 2007) Amazon.co.uk: Colossal Cracks: Montgomery's 21st Army Group in Northwest Europe, 1944-45 (Stackpole Military History): Montgomery's 21st Army Group in Northwest Europe, 1944-45 (Stackpole Military History): Stephen Ashley Hart: Books
I bought this when it first came out as at the time it was the only 'revisionist' text taking a fresh approach to the Normandy campaign. It cost be an arm and a leg in HB, but pleased to see it is now available in PB and at a good price on Amazon. Personally I think it has been bettered with material by the likes of Terry Copp, but well worth a look.