Why the Usual Suspects annoys me, and the author's implicit contract with their audience

I have never really cared for the ending of The Usual Suspects, although I know that a lot of folk do like it. For me it undermined what went before, and I felt rather cheated and annoyed as a result. 

I suppose that the audience is making an investment in any work of linear narrative work of art that they are participating in. If you sit down to watch a film or play or read a book, then you are forced to follow the linear narrative, and even if it is enjoyable enough going, then you do feel that you are making a certain sacrifice. That there is a certain implicit contract, that you expect things to resolve themselves in the expected manner, or in a satisfyingly novel manner. That is why not many people will embark on reading a book that they know to be unfinished, for example the Mystery of Edwin Drood, and no one would expect to publish a half written book. 

There are certain writerly conventions, for example

with a Philip K Dick book with various nested narratives, you might expect this nesting to continue. In a more conventional piece of romantic fiction then you might not;

by and large something will stick to the genre it started as, there are relatively few popular exceptions, such as Dusk Till Dawn;

the level of descriptive detail will generally be sustained throughout, though some modernist works will mention major events almost in passing, the end of The Magic Mountain, or Proust do this;

you are expected to read the entire work from beginning to end, though some authors deliberately insert random text to force you to skim, for example Douglas Coupland;

improbable aspects are introduced at the start of the work, rather than the end; 

The reader not only invests time, they also invest belief in the characters and situations, so while there might be some scope to play with the ‘reality’ of what is being relayed, too much undermining of the credibility of the story will just annoy the reader, unless there was never really any reality in the first place. With certain authors you know that you are in slippery territory when you start, Italo Calvino, Jorge Luis Borges, Vladimir Nabokov, George Perec, some science fiction. While the author might be clever inserting themselves as a character, or lyrics from popular songs, or jokey names for characters, or even parallels to historical events, for the reader these can strain the credibility of the piece and undermine it. The reader wants to be entertained, but they want to be laughing at the joke, rather than being the butt of the joke. For me, this also means avoiding any overt use of imagery, so no obvious allusions to Shakespearian plots, or classic literature, instead plausibility should be the benchmark of what is being described. 

In terms of plausibility there is either a sort of psychological plausibility, that is how you feel the world is, or a physical plausibility, that is how you see that the world is. So Kafka might be psychologically plausible, while lacking physical plausibility.