When you get right down to it, AC/DC might be the most reliable band on the planet. In 40 years, they never once challenged fans with anything other than straight-up, uncomplicated rock ‘n’ roll played with fuss-free intensity. They never made a concept album. They never dabbled in pop, R&B, hip-hop or electronic music. And they never swerved from their playbook of barroom-meets-arena swagger dosed with a shot of heavy blues.