Simon Chadwick's
Early Gaelic Harp Emporium

Historical Harps by Schola Cantorum Basiliensis

ed. Heidrun Rosenzweig
Historische Harfen / Historical Harps
Schola Cantorum Basiliensis, 1991
A collection of essays, each essay either in English with German summary, or in German with English summary. The essays cover many aspects of historical harps, from playing technique through to repertory and instrument design and construction. There is no content specifically related to the Gaelic harp traditions of Ireland and Scotland but there is a lot of very useful background information, and lots of nice b/w illustrations. New paperback, 203 pages.
£50 +