United Counties Buses - A Fleet History begins by taking a brief look at the expansion of the United Counties Omnibus Company since its formation in September 1921 through to its demise in October 2014. The company acquired over fifty independent operators between 1922 and 1938 giving the company prominence in Northamptonshire and surrounding areas. May 1952 saw the fleet double in size with the acquisition of the Midland area of the Eastern National Omnibus Company, encompassing Bedfordshire, north Buckinghamshire and north Hertfordshire. The National Bus Company split United Counties into three operating companies in 1986, United Counties, Luton & District and MK Citybus, halving the size of the fleet. After being acquired by the Stagecoach Group in 1987, the company was largely left untouched.

The main focus of the book looks at the vehicles operated by the company, covering the numerous types operated by United Counties themselves. The various liveries, both fleet and advertising liveries are also listed with in the book.