Hmm. Are there any books I'd like to unread? I can only think of one at the moment, which was a sequel too far. I fell in love with the British mini-series Flambards when it was broadcast on PBS sometime in the early 1980s. I sought out the book, which turned out to be a trilogy, published in America as a single volume. This, too, was wonderful.
Then one dark day at the library I found another sequel to the story, menacingly titled Flambards Divided. Well, you just have to wonder when an author writes a fourth book of a trilogy. All the signs and portents pointed to dirty work being done at Flambards, and they did not lie. All the ends that were neatly, and satisfyingly, tied up at the end of the third volume were undone, even shredded, by the fourth.
I have done my best to forget that horror of a novel. For a long time it destroyed my enjoyment of the original story, but now that sequel from hell has faded from memory. I think if I could find Flambards again, I could read it again, with no shadow from that literary doppelganger to dim the pleasure. But it took a couple of decades to reach this point.
Unreading is really hard.