Check out Sci-Fi Bokhandeln as well. They have friendly staff, and a good selection of english books and geek-stuff. Tabletop section is a bit meagre, but it still is worth a visit if you have the time. (
www.sfbok.se / Västerlånggatan 48)
As far as pubs and restaurants,
LMK what you're interested in. There's a pretty good selection of fine dining as well as more local joints.
Where will you be staying? If within Stockholm I'll hook you up with some places to eat lunch and have a coffee as well.
I'd definitely visit Debaser (check debaser.se to see if there's any bands playing) at the bridge between Gamla Stan (Old Town) and Slussen. Preferrably after visiting Sci-Fi Bok.
They have a pretty nice outside area with more contemporary indie music. Pretty young crowd though, but they serve Pims(!) and it's usually pretty relaxed (when it's not overcrowded).
I'd stay away from Gamla Stan and Drottninggatan, unless you want to do the tourist thingie.
Stureplan is the more upscale area for nightlife, to me it's kinda boring, but if you love that stuff (as well as standing in endless queues to get in) that's the place to go to with a ton of restaurants and clubs withing walking distance.
As said,
LMK what you wanna do and I'll get you a bunch of alternatives.