It was very interesting! The only thing that would have made it better is if Tolkien himself would have been able to work on it. There was a fair amount of (educated) guesswork, and there were some undefined words in dictionary, but it was still fascinating to read about the word and grammar structure and histories of his languages.
I would give this book 5,000 stars if I could. If you are at all interested in Tolkien's languages, or gathering context on how his world was built, you want/need this book. As with our actual world, language can help tell the story of a society, and it is no different for Middle Earth. This book is one of my prized possessions for sentimental reasons, as it has been with me almost as long as I first wandered into this "universe" shortly after seeing The Fellowship of the Ring on DVD. I was probably around 12 years old at the time. Do not be surprised when some of these words/phrases find their way into your own vernacular.
Cool and interesting, though not exhaustive. Author's descriptions get a little muddy at times, but overall she's pretty clear in her explanations. The bulk of the text is glossaries, so if you don't like those, be warned.
Geek alert, this is a very niche book. But as I am preparing to read the Silmarillion, which I could not get through five decades ago due to my youth, I thought it would be valuable. It is a linguists delight, and as someone who loves etymology, it is helpful to me. The author goes through many languages of middle-earth (although I wish Entish was in here, it is not) with tenses, rules, and the like. A reasonably detailed and helpful dictionary with fourteen of the Tolkien languages finishes up the book. It is well cross-referenced for its time, this being written prior to more powerful computer programs. And yes, I read the dictionary portion word by word. Anyhow, a must for Tolkien devotees.
A lovely introduction to Tolkien's many made-up languages. Though not in-depth on any one of the languages, it is nonetheless an excellent starting place for anyone wanting to learn more about the languages of Middle Earth!