Tokyo guide books
Your best bet is either at a bookstore in your home country before you leave or using resources on the Internet.
If you get to Japan without a guide, there are several other options: The airports (Narita and/or Haneda) have English language book stores and there are a number of stores in the city that have English language books and maps.
Kinokuniya in Shinjuku, 6th floor (sorry - website is in Japanese only): http://www.kinokuniya.co.jp/contents/pc/store/Shinjuku-South-Store/floorguide.html
And, if you find yourself in Yokohama, you can find books in Eigo here:
Landmark Tower Kumazawa