I’m more than halfway through Melville’s Moby Dick, and quipped to my wife that “…and he hasn’t even shown up yet!”
It made me think about all the other characters who barely appear, or even don’t appear, in a work named after them. Moby Dick only shows up at the end of Melville’s book.
The classic case is probably Samuel Beckett’s play Waiting for Godot, where – damn the spoilers, full speed ahead! – Godot never appears.
Dracula is mostly offstage in Bram Stoker’s book about him. He’s in the Transylvania section, of course, but once the scene shifts to England we concentrate mostly on the other characters.
We similarly track the effects of the monster in Frankenstein through his effects and Victor’s efforts to deal with him, but a.) The novel is named after Victor Frankenstein, not the creature. and b.) We still get a lot more of the Creature in his book than we do of Dracula in Stoker’s work.
I know there are lots of other examples, but I can’t think of them right now. But I have no doubt that Dopers have lots of other suggestions.
Horus doesn’t appear all that much in the Horus Heresy.
In the last set of books (The Siege of Terra) he spends all of his time communing with daemons and psychically harassing the Emperor (who himself is absent from most of the series and in the 40K follow up).
That’s sort of a special case. The play was never supposed to have anything to do with Virginia Woolf, and Albee was going to call it Walpurgisnacht, but reportedly saw “Who’s Afraid of Virginia Woolf”?" as a piece of grafitti, and liked it so much he changed the title. It’s a play, of course, on “Who’s Afraid of the Big Bad Wolf?” , the song in the Disney “Silly Symphony” cartoon The Three Little Pigs that was surprisingly popular when released in 1933 (according to Wikipedia, it’s considered the most successful cartoon short ever made).
Henry IV, Part 2. The king shows up for the first time in Act 3, and dies in Act 4. He appears in two or maybe three scenes, depending on where a given editor puts the scene breaks, and for a good chunk of one of them he’s asleep.
Honorable mention: Julius Caesar, in which the title character gets to do a little more stuff, but still gets stabbed a little less than halfway through the play.