First is The Battles of Lansdown and Roundway 1643 by Robert Morris (ISBN1858040132) and published by Stuart Press. This is a great little book providing a detailed account of the campaign and wonderfully a list of all the regiments and where known the officers therein. Absolutely invaluable and part of a large series detailing many ECW engagements.
Next are a couple of books by Bath's tame seventeenth century historian Dr. John Wroughton. We are particularly lucky in this area to have such an ECW enthusiast in residence, and even more so in that Dr. Wroughton is a staunch Parliament supporter (huzzah!). If I remember correctly he had a bust of Cromwell in his office as deputy head of my old school (luckily I was never called into the office when he became Headmaster but I expect it was still there).
A Community at War (ISBN095202490X) is a detailed study of Bath and North Somerset during the Civil Wars and contains a good chapter on Lansdown. This is is widely expanded in The Battle of Lansdown 1643 an explorers guide (ISBN9780952024989), which goes over much of the same ground but contains a useful section of the battlefield today. The latter book is not without faults eg. musket rests being referred to as 'lintocks' (sic), and has the air of being banged out in a bit of a hurry, but nevertheless worth getting hold of. Interestingly whereas Dr. Wroughton has previously always been quite emphatic about Lansdown being a Parliamentarian victory in this later book he is not quite so clear cut about it.
before the ambush and skirmish at Monkton Farleigh and Claverton (if I get out of work in time to get up there with the camera!).