This is an interesting question by Alec Stapp. What books are widely popular but regarded by scholars or experts within their respective fields as bunk?
I have expertise in nothing, but the question reminds me of The Age of Arthur by John Morris. It's a history of early medieval Britain. The author, a highly respected historian, argues for the historicity of Arthur as an actual person. Although widely read, other historians regard it as preposterous and the work greatly damaged Morris's reputation.
Reading it, I could understand why. Morris describes historical records of various Celtic warlords in Fifth Century Britain and leaps to the conclusion these necessarily describe a real Arthur instead of, well, just various Celtic warlords.
More generally, I'm skeptical of general purpose public intellectuals. I think it's impossible to be an expert in more than one field, so I hesitate to give credence to scholars writing or speaking outside of their expertise. And we should not underestimate the capacity of experts to be wrong.
What books do you think should be on an anti-reading list as defined by Sam Enright?
(Not just books that you don't like.)