Disclosure: I have owned and used only one other travel book in my life, so I don't have much to compare this one too. I am simply giving my impressions as a novice travel planner.
First off, I actually went to Japan!! This year! I spent 6 weeks in the Kansai region for a language program, and I traveled to Osaka, Kyoto, Nara, Tokyo, Shirakawa-go, Takayama, Gifu, Inuyama, Hiroshima, Himeiji, Sekigahara, Mt. Koya, and Mt. Hiei. I got this book before I left, but unfortunately forgot to take it with me. I did read the entire section on the Kansai region and some highlights of Gifu prefecture before I left. So as you might guess, my review will focus heavily on the section of the book featuring the Kansai region.
The book is nicely arranged: it starts out with some important things to know, gives some suggested itineraries, and then presents places to visit divided by region. Each region contains a regional map and a list of highlights of the region. It is then divided into cities in the region, giving some history, maps, and general information, before listing the attractions.
At the back of the book is a valuable little section called "Japan in Focus". It explains some about the history of Japan, the food, and various aspects of travel that are useful to know (such as explaining ryokan and onsen). I missed this section the first time I went through the book (I thought it was just another region section). I think it would have been much better placed at the beginning of the book.
I do agree with some other reviewers; some of the attractions given prominent positions should have been smaller, while some of the attractions shoved into the background should have been brought forward, but I am sure not everyone would agree with me and you can't please everyone. I don't believe that anyone should rely on a single source of information when planning their trip. I used this book to get an idea of what was out there and places I might want to visit, then I did more extensive research online. This book isn't all that big, and that is one of the things I like about it - it is very portable. And for its size, I think that it did an excellent job of choosing which attractions it included. One thing I do concede is that it spent too many pages on Kyoto. Of the number of pages devoted to the Kansai region (home to tons of famous and beautiful historical sites), more than half is focused on Kyoto. I had mixed feelings about Kyoto. It did have many interesting places to visit, but after all the idealistic pictures I saw before going, I had expected a bit more. I think that if I had actually stayed in the city itself rather than take day trips from Osaka, I might have enjoyed it more.
Note: Kinkakuji is beautiful, but if you've seen a picture of it, then there isn't really much of a reason to see it in person. It looks just like its pictures - from all angles. It does have nice grounds though. Instead, visit Kiyomizu-dera!
If you plan on spending a few nights in the Kansai region, the Kansai Thru Pass is a must. The three day pass (currently 5,000¥, also available as a two-day pass for a little less) lets you ride trains and buses unlimitedly (though not JR lines) for approx $17 a day (and the days do not have to be consecutive!). The JR pass is awesome (must be purchase outside of Japan!), but only if you intend to do long distance travel. The book covers the JR pass quite well, but I had to scour the internet to find the KTP. WHY?! To get anywhere in Japan you have to take a train, but for some reason the only train pass that is advertised anywhere is the JR pass, which is a little over $300 for one consecutive week.
I loved the Kansai region, but my favorite part of Japan was the Central Honshu area, specifically the areas in the Japanese Alps. Takayama and Shirakawa-go (and Inuyama) were the highlight of my entire 6-week trip. The book's section on this area is not very long, but it contains the good general information, and the information on the bus from Takayama to Shirakawa-go was accurate.
One reviewer complains that the book inaccurately represents Japan as a inexpensive place to travel. I agree with them (though $100 is ridiculous), but I can also see why the book might make that statement. Admissions were generally below $5, if you stay in a youth hostel (pretty nice actually) it is about $35 a person, and if you get the train passes you can get all over the place for a relatively cheap price. Don't think that it will be cheaper to travel in Japan than it would be in America, but remember that America also doesn't have nearly the amount of cool stuff to see! My lodging was paid for by the program I was with, but outside of that I spent about $1200 the entire trip (6 weeks or 42 days), which averages a little under $30 a day. This includes all transportation, admittance, food, and souvenirs.
The last thing I have to say is that the color really mattered! I didn't think that it was all that important that a travel book have colored pictures (the last one I used didn't), and admittedly the color didn't reveal any missing details, but seeing the images in color just made it seem more real and made me much more excited about going to the places pictured. I also think that it made the maps easier to read.