Every novel is a promise. The writer makes a promise to readers that it will be worth spending their precious time getting to know a book’s characters, settings, and intricate plotlines. In return, there’s supposed to be a big fat juicy payoff waiting for them at the end.

Good endings stay with readers forever. Readers probably remember their favorite endings. Some may have changed their lives. Unfortunately, bad endings stick with readers, too. How many times have you heard a book described as “great—up until the end”?

A bad ending is a broken promise, and it leaves a bad taste in the reader’s mouth. Bad endings produce bad vibes, which turn into negative reviews. If readers tell their friends that the ending sucked, sales will quickly dry up.

Each genre has rules, formats, and endings that fans expect. Readers assume that a mystery novel will end when the case is solved. Romances normally end when the two main characters fall in love. Writers can bend the rules but shouldn’t break them.

An underwhelming ending might not ruin a book. However, an ending that undermines the rest of the plot or the characters will lose readers. For writers determined to ruin their novels by killing the endings, here are five tips.

1. Tie pretty bows

Sometimes writers tie up every single loose end conscientiously and consistently. Readers know the feeling—a kind of sticky, glutinous kitsch where everything works out just right. Great novels tend to leave a little mystery and ambiguity, giving readers space to take an ending and make it their own.

2. Lazybones

Fans are quick to sniff out a rushed ending, and one can easily ruin all an author’s previous hard work. Just think of HBO’s Game of Thrones.

After two years of working on a book, an author might be eager to be done with it and move on to the next great idea. Rushing the ending is a great way to ruin a good setup. Writers are better served spending their time thinking about alternatives. Can a book end sooner? Has the protagonist solved the fundamental conflict driving them through the story structure? After the opening, the ending should take the most work.

3. Lord of the Rings it

After reading a thousand pages about hobbits and orcs and fiery eyes, readers are willing to accept a few different endings. J.R.R. Tolkien gets a little room for self-indulgence. For those who aren’t Tolkien, more concrete decisions are a necessity.

Writing 20 different endings and including them all, will most likely bore hard-earned readers to the point where they’re throwing the book at the wall just to be done with it. Authors need to nail their endings but not overdo them. Haruki Murakami is a master at this.

4. Deus ex machina

Sometimes it’s hard for readers to see a way out for the protagonist at the end. How are they possibly going to get out of this mess alive? Then something occurs that’s so impossible that readers are left feeling like fools. If there’s no possible way to have predicted an ending, it’s not satisfying. It suggests that the author was faking it the whole time, riding a plot with no direction. If there’s a deus ex machina, readers will desert a book and maybe even its author.

5. It was all a dream

The single worst way to end a book is by having a protagonist wake up and realize that it was all a dream. If an author plays that card, their book will not only be chucked at the wall but tossed on a big bonfire with an effigy of the author, the laziest writer of all time. Ten-year-olds know it’s a cop out; so should grown up authors.

Save the best till last

Once an author has finished a novel, I suggest they ask, is the story so good that readers won’t mind a bad ending? More often than not, it’s the ending that makes or breaks a novel. It might take a little blood, sweat, and tears to figure it out, but it’s worth it.

Rachael Cooper is the SEO and publishing manager for Jericho Writers, a writers services company based in the U.K. and U.S.