I asked my Taiwanese friend & she said there're very few if not very little of such Book Off ish shops in Taiwan that sell 2nd hand Japanese items
Even if so , she will not recommend you to go as they're not very reliable . Most Taiwanese would rather buy 2nd hand items from the 2 major Taiwanese online sites
Which're :
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http://www.ruten.com.tw/
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http://tw.bid.yahoo.com/
My friend has a friend who went to such a store a while back ago but in the end , she gave up as the place was so run down if not very messy