Th is has been asked so many times and answered so many times!!

You can get it all from stephenie meyers website!

Twilight: "The apple on the cover of Twilight represents "forbidden fruit." I used the scripture from Genesis (located just after the table of contents) because I loved the phrase "the fruit of the knowledge of good and evil." Isn't this exactly what Bella ends up with? A working knowledge of what good is, and what evil is. The nice thing about the apple is it has so many symbolic roots. You've got the apple in Snow White, one bite and you're frozen forever in a state of not-quite-death... Then you have Paris and the golden apple in Greek mythology—look how much trouble that started. Apples are quite the versatile fruit. In the end, I love the beautiful simplicity of the picture. To me it says: choice." source: stephenie meyer

New Moon: That is a ruffled tulip. Covers, for are mostly up to the publisher and the marketing and sales departments. So stephenie meyer does not know what the tulip means— she didn't have anything to do with this one.

Eclipse: The ribbin means breaking ties, Bella and Jake.

[Edit]You can get all of this from stephenie meyers website which is where i got this!!! link

New Moon: I think I found the reason last week when I had to find out more about tulips for my art class.

Legend tells of a Persian youth, named Ferhad, who fell in love with a young woman named Shirin. She did not reciprocate his feelings for her, so he went out into the desert to die, presumably from a broken heart. As his heart ached, his tears fell into the sand and turned into beautiful tulips. Amongst the Persians, the tulip is an offering a young man makes to his beloved. What he is saying in the Language of Flowers is "as the redness of this flower, I am on fire with love."