Written prior to 1900? Yes.

Written in English? Yes.

Philosophical? The best answer is No, although there is a connection.
History? The best answer is No, although there is a connection.
Decline and Fall of the Roman Empire? No. (Some audience laughter.)
Single author? Yes.

Checking one assumption...

Single book? No.

Periodical? No.
Entoeuvre? No.

Poetry? Yes. The audience puts down their phones and applauds.
Composer’s works? No.

So it's the title of a work of poetry written before 1900 (and possibly much older). It is not the author's entire work, but it is more than one book while not being a collection, and it doesn't begin with P. There are connections through the title to A, M, and V, as well as to legends in a way.

Bismarck's recap is mostly right. However, I did not say the AOTC was more than one book. I said it was not a single book. I'll also tell you for free that I was thinking of the main animal connection as being the author, and the main vegetable connection as paper. The mineral connection, which has not been explored, has—as already noted—Animal and Vegetable subconnections, and various subsubconnections.

Virgil? No.
Spenser? No.

English author? Yes.

Medium other than a book? No. I mean, like everything else, it now also exists on the internet, but otherwise you’d normally expect to find it in a book.

Post-Chaucer? Yes.

Victorian? No.
Kipling? No.

Shakespearean? No.

Written before 1/1/1? Yes. (We already knew that.)

Georgian? Yes.

Trying to be less boring. :)

Popeish? No.
Seabirds? No. (Except perhaps implicitly and very tangentially. Which means you should forget I even mentioned it.)