The Victoria County History of Kent
Three red volumes were produced between 1908 and 1932, after which work ceased in the county until 1999 when work resumed in conjunction with the University of Greenwich.
Kent was part of the Heritage Lottery Fund, ‘England’s Past for Everyone’, which produced a paperback book on the lower Medway Valley entitled, The Medway Valley: A Kent Landscape Transformed, authored by Dr Andrew Hann and spawned a continuation project which has seen Dr Sandra Dunster complete work on the towns of the lower Medway. The Medway Towns: River, Docks and Urban Life was published in 2013.
Part of Volume II, detailing the county's medieval religious houses, is on British History Online. For full access to all volumes, check your local library catalogue or your local archive.