Here are some other examples to muse on, from current historical novels. Subjects for biographical novels are usually straightforward, but for those with fictional characters, literary fiction, "novels of ideas," etc., the catalogers can be quite creative.
Subject headings for Dan Simmons' The Terror:
Survival after airplane accidents, shipwrecks, etc. -- Fiction.
Sea monsters -- Fiction.
For Judith Merkle Riley's The Water-Devil:
Forced marriages -- Fiction.
Women mystics -- Fiction.
For G.W. (Gordon) Dahlquist's The Glass Books of the Dream Eaters:
Rejection (Psychology) -- Fiction.
For Brenda Rickman Vantrease's The Mercy Seller:
Illumination of books and manuscripts -- Fiction.
For David Gemmell's Shield of Thunder:
Troy (Extinct city) -- Fiction.
For Heather Terrell's The Chrysalis (which may be a modern novel about WWII, haven't checked yet):
Art treasures in war -- Fiction.
World War, 1939-1945 -- Destruction and pillage -- Europe -- Fiction.
See, there are Library of Congress subject headings for just about everything. (Back to my more content-intensive posts once my work and HNS schedule lightens up, I hope.)