There is an article on a writer named Bette Howland, in the latest NYRB, which deflates her reputation. Elaine Blair, the author, offers a balanced and fairly critical assessment of this writer, a friend and disciple of Saul Bellow, whom I hadn't heard of myself. (I've heard of Bellow, but not Howland). Howland is not terrible, according the article, just not wonderful either.
It might seem counterintuitive to devote so many words to a forgotten and mediocre writer, if that's what Howland is. Part of the point, though, is to counteract the excessive praise Howland has gotten (though I was unaware of this praise myself, and many other readers are also unaware, I would guess.). The larger point is that not every forgotten figure deserves rescuing.
The problem with mediocrity is not that it exists. By definition, more things will cluster around the statistical mean (or below it) than will be excellent. We can't all be above average. A mediocre scholar will still be in the top 2% in terms of educational attainment, but within this 2% most of us will cluster in the middle. People who publish a lot will be the top percentiles of that 2%, and within that group there will be a statistical distribution once again. So maybe just being a scholar in the first place is enough.
As an accusation, mediocrity only makes sense if something is overpraised in the first place. So maybe Mayhew's first book on Lorca has all this praise, and I read it and it's ho hum for me. So Mayhew is overrated. I'm sure that within the select category of books published by U of Chicago P, mine falls somewhere in the average range.