For me, it’s Jude the Obscure. That book is easily the worst book I have ever read, without a single redeeming quality, other than that it finally ends. I only finished it because Far from the Madding Crowd was so damn good.
But really, Jude is the gold standard of awful books, in my opinion.
What’s your so-awful-it-deserves-shelf-space book, if you have one?
Or am I just weird?
The Last Shadow by Orson Scott Card. What makes it horrible is that it was greatly anticipated and wraps up the other 10 novels and joins two separate timelines of the same universe - except without tying up ANY loose ends with plot. Absolutely nothing is solved in the final book and all the build up from each timeline is completely wasted in a wishy washy “conclusion” that leaves a looooooot to be desired. This is why you don’t take decades to write the final addition to your extensive universe.