The postman`s just arrived with my copy of <I>Brecknock: Later Prehistoric Monuments and Unenclosed Settlements to 1000 AD.</I>(329 pages. Hardback)
Normally £48, presently £9.95
http://www.oxbowbooks.com/bookinfo.cfm?&ID=15513
I don`t think you`ll find a more comprehensive book on the Brecon Beacons than this one.
Everything`s in it, palaeolithic sites, caves, chambered tombs, barrows, cairns, stone circles, stone rows, standing stones, burnt mounds and settlements.....all of them.
baz