This is a list supplied by The Trail Riders Fellowship detailing books about unsurfaced carriageways. Most are general books about roads, all are a good read.

Exploring Green Roads and Lanes of Great Britain, Ian Thompson; Haynes.
Roads and Tracks of Britain, ?
The Making of the English ?
The Romance of the Road, ?
Roads & Road Transport, Hammersley, Basford.
Roman Roads in Britain, Margary, Baker.
The Rolling Road, Strong; Hutchinson.
Property & Landscape, Williamson & Bellamy; Phillips.
The Story of the Road, Gregory; Black.
The Road Goes On, Scott-Gile; Epworth.
The Old Roads of England, Addison; Batsford.
The Green Roads of England, Hippisley-Cox; Methuen.
Highways & Byways of England, Wilkinson; Iliffe.
From Track to Bypass, Wilkinson; Methuen.
Roads & their Traffic, 1750-1850, Copeland; David & Charles.
Travel in England, Burke; Batsford.
The Sotry of the Roads, Hartmann; Routledge.
The Golden Road, Stanley; Dent.
A History of Roads, Hindley; Citadel.
The Road, Belloc; Hobson.
Roman Roads in Britain, Codrington, Sheldon.
Packhorse, Waggon & Post, Crofts; SSH.
Mediaeval Roads, Hindley, Shire.

Roads and Trackways of the Yorkshire Dales, Wright; Moorland.
– Wessex, Wright; and – the Lake District, Hindle, all Moorland.
Lost Roads of Wessex, Cochrane; David & Charles.
Peakland Roads & Trackways, Dodd & Dodd; Moorland.
The Old Roads of Dorset, Good; Commin.
The King’s Highway in Craven, Brigg: SR.
Road Transport in Cumbria in the 19^th Cent, Williams; Allen & Unwin.
The Old Coaching Days in Yorkshire, Bradley; Smith.
Walking the Roman Roads of Cumbria, Southworth; Hale.
Ancient Trackways of Wessex, Timperley & Brill; Phoenix.
Chalkways of S & SE England, Pyatt; David & Charles.
The Icknield Way, Thomas;Constable.
The Old Road, Belloc;Constable.
Green Roads in the Mid Pennines, Raistrick;Moorland.
New Ways through the Glens, Haldane; David & Charles.
The Drove Roads of Scotland, Haldane; David & Charles.

This list is provided courtesy of the TRF.