This is a great book and a welcome addition for my library of Biblical Hebrew study aids. It will be beneficial to students (and teachers) of Biblical Hebrew at almost any level of proficiency. It's great for research and reference purposes as well as vocabulary building. As far as building my vocabulary, I think it also helps and is certainly useful, but I personally learn the best through reading. I can read a word in a passage once and remember it because of the context, while I will struggle to remember a word even after running numerous times through my word list. But obviously everyone learns differently and for me reading happens to be the best way to pick up new words and make them stick.
As for the book, the authors provide plenty of lists and ways to organize words to allow for multiple focused approaches to building up Biblical Hebrew vocabulary -- for example a frequency based word list for words appearing at least 10 times, a word list arranged by a common root, lists of nouns, lists of verbs (all verbs alphabetically and arranged by a verb type and stem...), statistical distributions of occurrences, etc.... Although I do wish it had even more list, such as a list of all hapax words for each section of the Tanakh for example, I do realize that it is beyond the scope of this book as intended by the authors. I highly recommend this book.