You're right. My English major instincts made me try to think of it in terms of academic period/genre labels, and what you need are labels for describing the book. Having had more time to think about it: "contemporary" is too ambiguous. "Fiction written and set in [era name]" is a bit awkward but it succinctly and unambiguously identifies the relevant information. And it works for books from the 19th century as well as ones from the 20th and 21st centuries ("contemporary victorian" makes my head hurt).

(still waiting for proper nomenclature to emerge for describing the various literary eras of the mid-late 20th century, that doesn't just use a variant of the word "modern" or label things by decade).