John Well’s Phonetic Blog has a review of the book “Spoken Here: Travels among Threatened Languages.”
As mentioned in the review, the books’ author Mark Abley is not a linguist, but provides a range of information about threatened languages around the world.
A language isolate is one that cannot be demonstrated as being related to another language. English, for example, is related to Dutch, Frisian and German, and therefore is not an isolate.
Update: The blog post on John Well’s Phonetic Blog appears to have been taken down.