Book: Lunatic Lovers of Language

Many years ago, I posted a question about conlangs to sci.lang. One of
those who replied recommended the book Lunatic Lovers of Language by
Marina Yaguello, which is supposed to be about Tolkien's languages and
other conlangs. I have since tried to find this book, but with little
success. Until now. Today I noticed that it can be ordered from Amazon at
a price of approx. $40.

Before spending that kind of money, I would like to know what you people
think about the book. What does it contain? Is it worth the money? Is it
mostly about grammar? Vocabulary? The creative process? Something else?

Thanks in advance,

  /Fredrik