This book is very outdated and not entirely accurate. It really contains only a fraction of the available Tolkien language material, and there are some languages that nobody even knew existed when this work was published.The chapters about Dwarven names and those of the Hobbits and Rohhirim are good, though. As for the rest of the book, if you want up to date, accurate info, I advise you to go to Helge Fauskanger's excellent web-page, Ardalmbion [online] the biggest and best resource on the net or in print.