From the back cover:

The second of Britain's four-engined bombers to enter frontline service, Handley Page's Halifax has forever lived in the shadow of Avro's superb Lancaster. However, it was a Halifax which became the first RAF 'heavy' to drop bombs on Germany when No 35 Sqn raided Hamburg on the night of 12/13 March 1941. Between 1941-45, the Halifax completed some 75,532 sorties [compared with the Lancaster's 156,000] with Bomber Command alone, not to mention its sterling work as both a glider tug and paratroop carrier with the Airborne Forces, maritime patrol mount with Coastal Command and covert intruder with the SOE.