Additional spoilers for you:
* Vader is Luke's father
* Frodo makes it to Mt Doom
* Rosebud was the sled
Not everybody has read the book (or heard of it), but may have been exposed to marketing for the movie and be interested in watching it (or reading the book first). I think it's fair to show a spoiler warning for a movie that came out just this month.
Want to know how I know this?
http://joyhog.com/wp-content/uploads/2013/08/Enders-Game-pos...
"This is not a game."
Right there, on the poster, is literally the "twist".
They wrote the movie assuming you read the book. Sorry, but this isn't a spoiler.
So, you know, whatever, but yeah I think it's a spoiler.
But seriously, Frodo getting to Mount Doom is not a spoiler because it's expected. Vader being Luke's father is unavoidable in popular culture because people quote it all the time.
Ender's Game on the other hand has a huge twist and is obscure enough that it can remain hidden. It went unspoilt for me for probably 25 years, and it's not like the book was unknown to me during that time (I probably heard of it in 1993, but only read it in 2008).
* Jesus dies, but gets better.
