I do not know the book but I have heard about its author, Joan Corominas, one of the greatest Hispanic philologists. He was a Professor at the University of Chicago after being expelled from Spain by the Spanish Fascists.
The book deals with the Aranese language, spoken in the Aran Valley, now part of Catalonia, Spain. Aranese is a dialect of the Occitan group of southern French languages, related to Gascon. It is the official languages of the Aran Valley and one of the three official languages of Catalonia. It is taught at the Valley as first language but the Aranese are usually multilingual. A beautiful spot in the Pyrenees , with lots of old Romanesque churches. Manuel Cardona, Member National Academy of Sciences of the USA