I guess it depends on what your goals are.
If you're only looking for studying towards the exam, I guess it's sufficient.
I think I read somewhere about the book being a massive listing of vocab words
and readings for each kanji. Again, OK I guess if you're studying for the exam, but
don't expect it to do wonders for your conversations.
I'd say the best way to build vocabulary is by doing a lot of reading.
Find something in Japanese that you find interesting to read and stick with
it. Another thing you could do is watch TV shows without subtitles. After a
while, you'll be able to pick out phrases that you know you haven't heard
before. That's where I get a lot of my vocab from. And it definitely makes
you sound more like a native speaker.
Something that might also be interesting would be to go through the lists of vocab
with a native and have them mark off the words they think are useful to know.
I'd guess that maybe only 20% to 35% of the words are actually useful in rea life.
Also, Unicom publishes a JLPT reading exercise book called Reading 100. It's for JLPT Level 1 and 2. 100 short readings for practice and they contain a lot of grammar that'll appear on the exam. You might want to look at this.
Unicom books
http://www.unicom-lra.co.jp/ja/ja_e.html
Reading 100
http://www.unicom-lra.co.jp/ja/ja5_e.html#ja5_e
Douzo.