Twentieth-Century American Bestsellers.
I stumbled on a fascinating online resource from a 2006 class taught by John Unsworth, dean of the Graduate School of Library and Information Science at University of Illinois at Urbana-Champaign. It's a database of twentieth-century U.S. bestsellers, organized by author, with entries by his students. The entries include physical descriptions of the particular work, publication history, analysis of sales (if information is available), and quotes from reviews. The mystery-related works range from S. S. Van Dine's The Bishop Murder Case (1929), Daphne du Maurier's Rebecca (1938), and Michael Crichton's The Andromeda Strain (1969) to Agatha Christie's Sleeping Murder (1976), Tom Clancy's The Hunt for Red October (1984), and Mary Higgins Clark's Loves Music, Loves to Dance (1991).
It's interesting to look at the posted bestsellers list by decade (from Publishers Weekly and Bowker's Annual) for a peek into their eras: The two Theodore Roosevelt books in 1920 after his 1919 death; the over-the-top The Sheik by Edith M. Hull (1919; US publication 1921. "'Oh you brute! You brute!' she wailed, until his kisses silenced her"); the reappearing names of Winston Churchill, A. J. Cronin, Mary Roberts Rinehart, Rafael Sabatini, and others over several years.
The entries, it must be noted, vary in writing quality, and not all bestsellers are covered. However, as it can be difficult to find accurate information on such works, this resource is very helpful.