According to Publisher's Weekly, the bestselling book of 1900 was a historical romance called To Have and to Hold by Mary Johnston. It begins:

THE work of the day being over, I sat down upon my doorstep, pipe in hand, to rest awhile in the cool of the evening. Death is not more still than is this Virginian land in the hour when the sun has sunk away, and it is black beneath the trees, and the stars brighten slowly and softly, one by one. The birds that sing all day have hushed, and the horned owls, the monster frogs, and that strange and ominous fowl (if fowl it be, and not, as some assert, a spirit damned) which we English call the whippoorwill, are yet silent. Later the wolf will howl and the panther scream, but now there is no sound. The winds are laid, and the restless leaves droop and are quiet. The low lap of the water among the reeds is like the breathing of one who sleeps in his watch beside the dead.

In honor of Literary Kicks' look at pricing, I've done a little bit of research into the cost of books through the years. The first big book of the last century—chick lit, no less—seemed like a sensible place to start. First run as a serial in The Atlantic and released as a novel in February 1900, a small tidbit in The New York Times mentions that 270,000 copies of To Have and to Hold were in print by November. The next month, the Los Angeles Times reports the author's earnings as $40,000, roughly equivalent to just under a million dollars today.

Some other numbers:

To Have and to Hold by Mary Johnston
Houghton Mifflin, hardcover, 403 pages

List price in 1900: $1.50
Adjusted for 2007: $36.20

List price for a 2006 reprint (Vision Forum, hardcover, 440 pages): $24.00
Adjusted for 1900: $1.03

Price range of the first edition on Abebooks: $3.00 to $350.00
Adjusted for 1900: $0.12 to $14.50

Ebook download: free

Interesting. The passage of time has actually forced the price of this particular title downward. And you can't get much cheaper than free.