I like this book because it groups a lot of the basic vocabulary you need about specialized fields. You don't have to go searching through a dictionary to pick it all up. There is maybe one field where I feel fairly confident, but most of the rest I'm not that interested in and only want the vocabulary because I absolutely need it to listen to a lecture, read a book or the newspaper, or just talk to someone who I know will bring up a certain topic because it's in the news or it is their pet pieve.
The book is also useful because the author tries now and then to give hints on differences between certain words or groups of words. That's something you will definitely not find in a dictionary.
If you're a beginner, you can just read the commentary and look at the lists and pick up what you need, not try to memorize everything. If you're more advanced you can read the sample sentences. I definitely don't agree with those who say if you're intermediate or advanced, you can go out and read the books themselves, and don't need a book like this. I don't want to be reading many Japanese science books, but I still want to know how to say chemistry. The easier it is, the better, and this book does make it easier.