Train stations, convenient stores and book stores are few places where you can get maps & guidebooks
You can get a subway / train map at any train station. They are kept there - and could be in Japanese. You can ask for a English one.
You can also find road maps in any of the convenient stores. But they might be in Japanese. Then there are book stores like Yurindo - Kinokuniya etc where you can certainly find guidebook or maps.
Then there are few local newsletters or magazines in English eg. Metropolis magazine kept at most bars or they have a website too - where you can get guide to local food joints, places to visit, local festivals etc. So this is not a formal guidebook per say - but can certainly give insights into local happenings.
(attached is a Tokyo subway map - the different colors signify different train lines)