Outside Sapporo, finding English-language books and magazines is difficult, so you may want to browse in this expansive bookstore near the West Exit of Sapporo Station. Foreign magazines are on the first floor near the escalators, and fiction, nonfiction, and English-language teaching books are on the second floor. The children's section also has many Japanese titles in translation, and a decent selection of DVDs (although they're cheaper at Yodobashi Camera, just under the railway bridge on the same street). Kinokuniya is notorious for overcharging, so keep an eye on the exchange rate.
JR Sapporo Station, Kita 5 Nishi 5, Sapporo, 060-0005, Japan