No spoilers, but…the second and third books in the series (what gets published as “The Man in the Iron Mask” is something like the last quarter of the third book) play on this a lot.

The second book is called “Twenty Years After” and we see our middle-aged heroes figure out what each of them have grown into in the intervening years, what’s changed and what hasn’t. It’s an enormously underrated book.

A good way to find these authors: Wikipedia has lists of bestselling books in the US for every year from 1895 to the present.

Looking through the lists, for example, from 1900-1910, you see a few kinds of books:

• Books by authors who are still more or less famous (Edith Wharton, Booth Tarkington, Frank Norris, Upton Sinclair, Arthur Conan Doyle).

• Books you only recognise because someone made a film (The Virginians, The Clansman).

• Books by writers who are obscure but well regarded by academic specialists in that period (Mary Cholmondeley, George Barr McCutcheon).

• Everything else. A lot of the “everything else” will be by the kind of writer you’re looking for.