Pshaw!
Some of Salvatore's outright achieve (if not surpass) mediocrity!
I'll give you credit for being nice, in much the same way that a parent will watch second graders playing soccer and say, "Look, they are going after the ball! That's ... well, that's something. And little Salvatore ... I mean, he's holding down the defense by, um, sitting in the box and playing with dandelions."
But (unpopular opinion ahead) .... Salvatore could not surpass mediocrity on his best day. The one nice thing I will say about his literary output is that, to quote Uncle Joe, Quantity has a quality all its own.