This is Pred's 2nd book, the first was about the foundries and ironworks that the NW Wales slate quarrying industry spawned to support it. This book is about the slate processing industry - not the making of roofing slates at the quarries, but the making of slate products such as gravestones, cisterns to hold liquids, enameling slate slabs for electrical switchboards or fireplaces.
It's well worth having if you're interested in the slate mines and quarries, A4 sized, well researched, bilingual and lavishly illustrated...