A lot of the sites, including Amazon and B&N's websites have similar books, and people who bought this also bought areas on the pages for individual books. That's how I've found several different books series that I'm reading.Online, I'd be limited to books from any series that I currently know.
Why?
There are often recommendations from ST fans, right here, about great new and favourite authors and SF series. There are lots of ways to leave yourself open to trusted recommendations apart from casual browsing the shelves, although that's always fun.
As for B&N closing down stores, I really hope they don't close down the one near me. There are a couple others in town, but they're nowhere near as close as this one.
I actually buy pretty either as an e-book or at the Wal-Mart where I work. I own a Nook though, so I do go to the B&N store to get help whenever I have problems with it. I just hope the whole company doesn't go under, because I get pretty all of my e-books off their site.