Manga is certainly big part of it, but there was always a sizeable "text only" section as well - 20-30% maybe ? Manga 40-50% I would guess. And indeed, no shrinkwrapping (only exception - the 1000 yen series bundles, but thereit was for practical purposes :) ) and you can see a lot people reading at any time.
And its kinda necessary to find what your are lokking for, especially if you are a foreigner with shaky levels of reading Japanese. :) Also you can find interesting stuff you did not know existed just by picking a random book and looking inside. More so as each Book Off store seems to have different gems hidden inside - we visited quite a few (Kagoshima, Kawasaki, Akihabara) and each one had something special. :)
Oh, absolutely, as a foreigner in a Book Off I love the no-shrinkwrap policy and also the way it's a large and well-populated space that's much less intimidating to walk into than the kind of second hand bookshop that's practically empty and you feel like you're being observed by the old dude behind the counter... And they are indeed great too for buying "text-only" books -- I'm just not sure the business model would work anywhere near so well if the text-only section had to carry the whole thing without that 50% manga area.
Agreed about the regular local (in my case Czech Republic) used book shops - they are kinda like antiquities and totally different atmosphere. They also seems to buy & sell old and somehow interesting books - if you just want to sell a recently released novel or some text books good luck. As far as I can tell Book Off does not make such a distinctions.
Anyway, as a result there is really not a good place where to sell newer less interesting books to other people - there are some online Ebay like sites & I've heard people buy & sell used books over Facebook. Still far cry from basically going to a nearest Book Off with bags of books to sell (at least that's how I imagine it to work when you sell books to them ;-) ).
Maybe that could be something that would make it work here as well. It really seems like there is a complete "circle" for books in Japan but not here & Book Off seems to be a big part of that.
And its kinda necessary to find what your are lokking for, especially if you are a foreigner with shaky levels of reading Japanese. :) Also you can find interesting stuff you did not know existed just by picking a random book and looking inside. More so as each Book Off store seems to have different gems hidden inside - we visited quite a few (Kagoshima, Kawasaki, Akihabara) and each one had something special. :)