In general, I found this book a good addition to the list of those publications dealing with the sad and worrying issue of the disappearence of many of the world's languages.
The author is obviously sympathetic towards minority languages and is trying hard to come up with some practical arguments for their preservation.
However, I found 2 major shortcomings (?) in this book.
First, it contains a (too) long chapter on the theoritical question of what language actually is and how languages have developed. While this might be of interest to some, it isn't directly linked to the main topic, and may make some readers put the book down with boredom.
Secondly, it deals in greatest length with examples of language extinctions from the historical past: Latin 'killing' European languages, English 'killing' Celtic ones in centuries gone by. Again, these are of some interest, but have little to do with the situation today, when minority languages face unprecedented pressure from globalization, television and universal education, none of which were factors centuries ago.
Therefore I think the present/recent examples would have deserved more detailed coverage.
They do get some to be fair, but not as much as they should.
As usual, the emphasis among current examples is on native North American languages, a group already spoken by very few only, and mostly doomed.
There are also interesting examples mentioned from Australia - but described as mere anecdotes.
Finally, this book does give at least some coverage to countries where most of the presently still existing languages are being spoken under heavy pressure from a 'national language': eg. Indonesia, the Philippines or Nigeria. Unfortunately the interesting and complex situation in these countries receives a far less-detailed coverage.
All in all, this book is interesting and will hopefully go some way towards raising awareness of this important issue.
Because of the disproportionate emphasis on old history and the situation of minority languages in English-speaking countries, I would actually only rate it only 3-4 stars, but I gave it 5 to even out an unfair 1 star rating of a silly "review" (which has now been removed)long sitting below mine.