Bring a backpack. This is the place to spend an hour happily browsing before carrying off an embarrassingly heavy armful of the books you just had to have. They're especially rich in philosophy and religion and other scholarly nonfiction. This store isn't so big that you'll lose an entire afternoon there, which means you can justify visiting more often. I especially love coming in when the staff is sorting and pricing the contents of an estate sale haul, surrounding the front desk with boxes and heaps of unknown treasures with that inimitable private-library scent of dignified decay. I'd pay them to let me help out, not even kidding.
Do check the hours on their main website, rather than Google. The Jewish Sabbath and holidays are observed, so you'll need to get there before sundown on Fridays and plan on a nighttime visit on Saturdays--they stay open late then, so stroll over after dinner.