Reviewing self-published books is a wonderful job, but much of my time is spent reading work that doesn't even rise to the level of a competent first draft. Spelling and grammatical errors abound, the nonfiction is impassioned but unfocused and the novels are often just a disaster. But there's a lot to be learned by reading them.
If the giant hand of God is visible moving a character from place to place or flicking them forward in time, there's something to be learned by analyzing the failure. When a novel is well-crafted it's almost as though everyone is gliding along on invisible treadmills. Seeing the same thing done wrong can help attune you to how better authors do it so well.
I just finished a 500-plus page thriller that was compulsively readable despite being a train wreck. One character had a nervous stomach, and the whole story ground to a halt no less than a dozen times while he ponderously chewed an antacid so we'd know something scary was about to happen. I stayed up past my bedtime with this book because I still wanted to know what would happen, but halfway through that roll of Tums I also started rewriting things mentally.
First of all, I'd let some other characters signal suspense so we're not always looking at Barfy for his reaction. And he could break things up a little, too, simply by wringing his hands or expressing more general agitation. The main character had an obvious "tell" as well, a physical tic that gave readers too big a clue as to the nature of her problem. By the time the big reveal came, it was a nonissue, and things went quickly downhill from there. But it was easy to see how to scale back those foreshadowing scenes and build more thrills into this thriller.
If given the choice, always read things you enjoy. But don't think a bad book has nothing to teach you; understanding how and why things go wrong is a tonic. Let it prevent you from making the same mistakes.