Powell's Technical Books used to be my favorite place to hang out. I would ride downtown in the morning and spend an entire day there, scanning every shelf in my fields of interest, reveling in periodic hits of serendipity. Since PTB closed, I've been back once. It wasn't worth it any more. I'll admit that I did like it better back before the store was spruced up to be like a Borders.
How is it like Borders? It's a warren of different rooms on different floors, half of which are more like a warehouse than a retail store, with a huge selection of used and new books shelved together. I loved the separate technical books stores, too, although they still have a great tech section in the main location. I assume the standalone PTBs shrank then closed because people were browsing more than buying.
Should’ve charged a modest fee for the periodic hits of serendipity.