Borderlands is hyperfocused. I'd suggest you need to be MORE focused, your stock is spread out. I'd suggest you drop every area you're not amazing with.
You need instore events that draws in the people who read your new more focused stock. Borderlands has a constant stream of author readings, signing etc. that bring people into their store.
I can't tell if you're doing this, but you need to be selling outside of your bookstore at trade shows, speaker events etc. When the Grand Rapids economic club has a speaker who has written a book, our local store has a table full of them for sale and clears $3-800 per event in sales.
Borderlands made a fundraising appeal to their customers a few years ago. The pitch was invest in us with a Gift Certificate that can't be redeemed for a year, but got a discount when used. It gave them a nice slug of working capital while they were expanding and more than a few customers dedided to simply hold onto the certificates to support the store they loved.
You also really need to take a sharp look at you business, figure out what bits contribute and what parts don't. Some basic business analysis can often do wonders for a business.