[samurai007]

There's a large shopping complex under Namba station with quite a few good places to eat, and there is also a covered above ground mall just north/northeast of Namba station. I'm not sure if it's still there, but one of the better used manga stores is just south of Namba station (in fact, just south of the Osaka Hard Rock Cafe behind Namba).

The other great used manga store in Osaka is in the northern part, near Osaka station. Take the subway from Namba to Osaka station, climb up to ground level, and head to a covered shopping walkway southeast of the station, the used manga store was several blocks south in there.

I loved exploring the used manga shops because a) they had many titles you couldn't find in a regular bookstore, and b) the books were usually about 1/2 cover price!