What's the meaning of the word in this sentence?
This year marks exactly two countries since the publication of Frankenstein; or, The Modern Prometheus, by Mary Shelley. Even before the invention of the electric light bulb, the author produced a remarkable work of speculative fiction that would foreshadow many ethical questions to be raised by technologies yet to come.

This year marks exactly two countries...... two countries? I don't understand. The followings are two books, aren't they? Why countires?

Question

What's the meaning of the word in this sentence?
This year marks exactly two countries since the publication of Frankenstein; or, The Modern Prometheus, by Mary Shelley. Even before the invention of the electric light bulb, the author produced a remarkable work of speculative fiction that would foreshadow many ethical questions to be raised by technologies yet to come.

This year marks exactly two countries...... two countries? I don't understand. The followings are two books, aren't they? Why countires?

Answer

Evelyn is correct -- it should definitely say "centuries," not "countries."  It's been slightly over two centuries now since Frankenstein was published.

(It's just one book, not two.  The original title of Mary Shelley's novel is "Frankenstein; or, The Modern Prometheus."  We usually just call it "Frankenstein" now.)

Answer

I think it's supposed to say "centuries", not "countries". One century is 100 years.