Jimbocho
This was a bit of a let down for me. This is meant to be "book town", and it is, there are lots of book shops, both new and used, but I think it's a bit overhyped.
What to do
Italia Shobo
I was really keen to get to this place that stocks italian language books, thought I could get some second hand novels etc. It was a pretty small selection, and also had Spanish, which is fine, but they weren't even sorted by language! So you do have to be pretty hot on quickly detecting between the two languages, which is kinda annoying when they are similar in certain respects.
Kitazawa Bookstore
I did like this. Be aware that for the second hand books you have to like go around the corner, into a building and upstairs that all feels a bit like "am I going the right way?!". You are. I found it difficult to browse with a child in tow, but if you can take the time in peace I think it's good. It was pretty expensive though.
Bumpodo
This was a nice stationery shop. We managed to get a few niche and nice things here, so I think it's worth a stop if you are in the area. It's not huge, but it is well curated and has some nice things.