American Book Exchange is more than the name implies. It’s also a nifty little piece of software, designed to lead the consumer to rare and out-of-print books with minimum effort. “It’ll change your life,” one La Jolla bookseller said idly a couple years ago—little did he know it and programs like it would become a key component in altering the life of San Diego as well. Wahrenbrock’s Book House, formerly located downtown at 726 Broadway, abruptly closed its doors July 31 after a 74-year run that featured a 2006 fire that destroyed nearly 25,000 books and a dwindling customer base amid Internet-sales inroads. The store also terminated its online service. Its 250,000-volume inventory is up for grabs, and owner Chuck Valverde Jr. is seeking buyers. Vernon Wahrenbrock opened the three-story venue in 1935. The store never quite recovered from the fire, whose aftermath kept it close nearly three months. It’s the latest casualty among an endangered species–the 109-year-old American Booksellers Association now has barely 2,000 members, down from about five times that number during World War II.