I've been waiting for a well-researched frequency dictionary of Japanese for a long time. This book is the only one of its kind, really, so there's not much to compare it to. It's really useful, with some caveats:
First, I wouldn't recommend this for beginners. I see this book as something for lower-intermediate and higher learners of Japanese, to help fill in vocabulary gaps efficiently. This book would be great for instructors and textbook authors as well, so they can gear their material to more useful words first.
Beginners need to learn more grammar before using this book, because many of the early entries are grammar-related "words"-- verb endings, postpositions (Japanese uses postpositions over our prepositions), etc.
Second, I wouldn't use this as my main dictionary. The definitions and example sentences are useful, but not exhaustive, and some words aren't easily defined or explained in just one sentence. (Try it with "of" or "in.")
You won't find anything else like it.
Thoroughly-researched, good explanation of research methodology used.
Entries listed by frequency of use
Sidebars explain other things like predominant pronunciations for words with multiple pronunciations.
Sidebars show frequency lists of specific useful topics. (Animals, transportation, etc.)
Statistical data with each entry.
Japanese-order index. (Not English alphabetical.)
Frequency lists by part of speech in the back.
Index of Word Types by origin (wago/kango/garaigo/kanseigo/proper names)
Cons (some are nitpicks, some aren't):
Entry headwords are kanji and romaaji only. No kana.
No furigana in sentences. (Makes it tough for beginners to pick up kanji readings.)
Sidebars are not indexed: you have to discover then as you go.
Japanese-order index doesn't have kana to help you sort out kanji entries, nor does it have romaaji. If you don't know the kanji reading, you may have trouble finding it.
Part of speech frequency lists lack kana/romaaji.
Index of Word Types by origin limited to first 1000 entries.
With those caveats, I wholeheartedly endorse this book. With a little careful editing, I think it could be a real gem. As it is, it's already very, very good, if you know how to use it.