It would be useful the read about all the cool places Japan has. How can you go see something nice if you don't know it exists? I'm going to visit Saitama prefacture so I read about it and found some really nice places to visit there.
I think a little understanding is useful. Language, customs, places... but you might want to get adventurous and go where the wind takes you. You can have fun either way.
..I think it's absolutely useful to read about any place your going to visit.
Why on earth wouldn't it be? I think it's not only useful, but also fun, to plan your trip etc. In a way I think it's also a godd manner to study about your destination, so that you won't be totally unaware of local specialities, ways etc, and that way offend the local people.
I've been dreaming about my trip to Japan for a couple of years (about 1 year with a more serious attitude), and I've been to Japanese language courses, Japanese aesthetics course, watching Japanese movies, listening to Japanese music, writing to my Japanese penpals etc..it has really sort of "opened" the door for me, and it has also just made me dream about and want this trip more and more. I just want to know more and more, and really _experience_ Japan
Now I have the Lonely Planets guide book for Kyoto always travelling with my in my bag, so that I can read it in buss/train etc. It's very useful, interesting and a fun book...I recommend it..