American books that, according to records, their blurbs, their authors, wikipedia, etc., appear to have been popular or well-regarded in their time, but have now faded into obscurity.

An Autobiographical Novel, for example, was apparently greeted with great enthusiasm; Rexroth was interviewed on the radio and on TV. On Goodreads it has fewer than fifty reviews.

(From the “Rivers of America” series I included just “The Everglades,” which I think was the most popular title, and "Great River: The Rio Grande in North American History," which won a Pulitzer for history in 1955. Apparently the entire series was extremely popular, so much so that its publishers extended it from the planned 24 volumes to an eventual 65 volumes over 37 years.)