The Kinokuniya bookstore is at the same spot as Mitsuwa (plus a few restaurants and Clover Bakery).
If you catch the 23 (south I think) in front of the convention center, it'll take you into Cupertino (about an hour - 45 minutes) to the Marukai Market on Stevens Creek Boulevard near Wolfe (in Idlewild Center). There's a Daiso next to it, Beard Papa, Yoshinoya beef bowl place across the street, Jo-Ann's Fabrics across the street too.
Yup, yup. Take 23 toward De Anza College and depart at Stevens Creek and Saratoga Ave. Depart the bus, cross Stevens Creek Blvd. and follow Saratoga Ave. It's about three blocks, over the 280 freeway, and then one more block and you'll see the Mitsuwa and Kinokuniya. If you're going to visit a Daiso in West San Jose, the one in the middle of the parking area here has a better selection of goods than the Cupertino store. Catch the return bus back on Stevens Creek on the opposite side of Saratoga Ave. - across from the McDonalds.
For Marukai and assorted stores you'd want to stay on 23 for another 10 minutes or so and depart at Stevens Creek and Portal Ave. The Marukai and the like will be on the other side of Stevens Creek - look for the big Merlion statue / fountain. Return bus will be right there in front of the Elephant Bar, across the street from Yoshinoya.
Better to hit both in the morning as 23's can be fairly crowded on the weekends but the buses run fairly frequently. Friday morning would be your best bet for a quick trip out and back in my opinion.