Single entendres and loud guitars. What's not to like?
It wouldn't be fair to call Back In Black shallow, but there's not really a lot of depth or complexity here, nor is it needed. Titles like "Shoot To Thrill", "Let Me Put My Love Into You" (sample lyric: "let me cut your cake with my knife") aren't exactly difficult to decode, and the music is just as straightforward. But that doesn't imply that it's without power, excitement or dynamics. Obviously it's great rock - you don't sell million and millions on the back of sub-standard music.
I'm not particularly keen on the high-register screech-sing of much of this kind of stuff but Brian Johnson's voice has enough grit and personality to make up for it. The guitars are superb, of course, thick, crunchy and powerful. Even better, it's ten good tracks and doesn't outstay it's welcome. Classic for a reason.