I'm an old reader who loved older books even when I was young. As such, I was horrified to discover that older books are almost totally unknown to younger readers. As best I understand it, Amazon and the remaining booksellers of the world focus mainly on new books; perhaps they don't make as much money on older literature.
But there are so many great older books out there. And I love those books. So I started recommending them over on Reddit. In the field of fantasy, for example, there are a million people recommending Brian Sanderson and nobody recommending the works of Lord Dunsany, Michael Moorcock, or Barry Hughart - among many other wonderful older fantasy authors.
Lord Dunsany in particular wrote a short piece that touches on this point:
THE RAFT-BUILDERS
All we who write put me in mind of sailors hastily making rafts upon doomed ships.
When we break up under the heavy years and go down into eternity with all that is ours our thoughts like small lost rafts float on awhile upon Oblivion's sea. They will not carry much over those tides, our names and a phrase or two and little else.
They that write as a trade to please the whim of the day, they are like sailors that work at the rafts only to warm their hands and to distract their thoughts from their certain doom; their rafts go all to pieces before the ship breaks up.
See now Oblivion shimmering all around us, its very tranquility deadlier than tempest. How little all our keels have troubled it. Time in its deeps swims like a monstrous whale; and, like a whale, feeds on the littlest things—small tunes and little unskilled songs of the olden, golden evenings—and anon turneth whale-like to overthrow whole ships.
See now the wreckage of Babylon floating idly, and something there that once was Nineveh; already their kings and queens are in the deeps among the weedy masses of old centuries that hide the sodden bulk of sunken Tyre and make a darkness round Persepolis.
For the rest I dimly see the forms of foundered ships on the sea-floor strewn with crowns.
Our ships were all unseaworthy from the first.
There goes the raft that Homer made for Helen.
The way I see it, recommending an older book to a new reader is helping a raft to float a little longer. What great old books do you like to recommend?
Roger Zelazny is one of my favorite authors. He turned me on to the poetry of A.E. Housman, too.
I must admit that I hated Jack Chalker for what he did in so many of his books: create sympathetic characters and then abuse them in unimaginably horrible ways. I was so angry that I almost walked up to him and told him off when he was the guest of honor at a local convention.
Almost.
If you haven't read Zelazny's Lord of Light, you should really check it out. It's generally considered his magnum opus. The only caveat is that there's a flashback that starts with the second chapter that lasts for more than half the book. Some people get confused by that!