Most Christians today are very unlike its intended audience; most of them never read it in large chunks, let alone straight through; most of them read it through several extra layers of interpretation that were almost certainly not present in the original (and which, in my opinion, detract from one of the chief literary merits of Mark, the sense of mystery it cultivates and maintains).
The gospel of Mark has tremendous literary merit.
“Tremendous” is rather generous. It does indeed have literary merit, but that’s hardly why it’s successful.
Do you have a reason to think that’s hardly why it’s successful?
Most Christians today are very unlike its intended audience; most of them never read it in large chunks, let alone straight through; most of them read it through several extra layers of interpretation that were almost certainly not present in the original (and which, in my opinion, detract from one of the chief literary merits of Mark, the sense of mystery it cultivates and maintains).