Edgehill 1642: The Campaign and the Battle Peter Young, Windrush, 1967. ISBN 0900075341. Classic battle account by Brigadier Young, founder of the Sealed Knot and successor to Firth and Davies as father of Civil War Regimental History. Contains histories of the Royalist and Parliamentarian regiments at Edgehill and reprints several useful contemporary tracts. A little dated now but still a great read.
Cheriton 1644: The Campaign and the Battle John Adair, Roundwood Press, 1973. Extensive detail on Hopton's and Waller's armies and their campaigns. Subsequent arguments about the exact battle site do not detract from the analysis of the armies.
Cropredy Bridge, 1644: The Campaign and the Battle Margaret Toynbee and Peter Young, Roundwood Press, 1970. Another classic, this time focussing on Waller's encounter with the King's Oxford Army.
Marston Moor 1644: The Campaign and the Battle Peter Young, Windrush Press, 1970. The decisive battle of the Civil Wars examined, with regimental details of the Marquis of Newcastle's, Prince Rupert's, the Earl of Leven's, Earl of Manchester's and Lord Fairfax's armies of 1644. Several discoveries have emerged since publication but this is still a valuable tome.
Naseby 1645: The Campaign and the Battle Peter Young, Century, 1985. ISBN 0712604898. Another major account with much regimental detail on the New Model and the Oxford Army, but not quite up to Young's earlier standards. Again several alternative interpretations have been proposed and further discoveries made since publication.
The Battle of Benburb 1646 Clive Hollick, Mercier Press, 2011. ISBN 978 1 85635 670 1. Owen Roe O' Neill's Irish Catholic Confederates' victory over Monro's Scots Covenanters and Ulster Protestants. Gives histories of the regiments involved in the campaign, particularly useful for O'Neill's army.
Ireland 1649-52 Cromwell's Protestant Crusade Michael McNally, Illustrated by Graham Turner, Campaign 213, Osprey Publishing, 2009. ISBN 978 1 84603 368 1. Well-illustrated introduction to Cromwell's Irish campaign.