At its very heart, at a mechanical level, the game involves the collection of identical Macguffins, with two player characters co-operating by passing items back and forth between them. On another level, it is an examination of two different lives, Ross and Helen, and the events that shape them. On a third level, there is a mysterious story that seems to involve two consciousnesses struggling to survive. It is not entirely clear how much of the story is "real" and how much takes place in a dreamscape; based on the two "winning" endings, I would suspect that absolutely none of the story, not even the opening scene, takes place in reality.
It is, of course, possible to ignore the second level altogether: one could simply collect the Macguffins and proceed to the endgame. One learns nothing about the characters that way, though I do get the impression that half the point is in discovering the histories of Ross and Helen.
On my initial playthrough, paying close attention to everything, every instance of memory, collecting the Macguffins for both Helen and Ross, I was able in the end to choose either of two endings. First: Ross lives and Helen dies, and there is also the implication that Ross's mother, Caroline, either lives or dies peacefully with her son at her side. Second: Helen lives and Ross dies, and Helen's stillborn child Sophie lives on as well.
On my second playthrough, I tried ignoring the memories and all of Helen's branch of the story. Surprisingly, the ending I got was the one in which Helen, not Ross, survived; this in spite of having made the endgame choice that initially had led to Ross's ending. There was a very brief cutscene set in a hospital -- I understood from my first playthrough that this was from Caroline's point of view, though it appeared this time that she was dying. The implication seems to be that Sophie is in fact the reincarnation of Caroline: Sophie lives only if Caroline dies, freeing her soul to find a new body.
Perhaps Ross and Helen are in fact the same soul, hesitating between two potential lives to be born into.
All this to say that the game rewards close examination and replaying. The winning sequence by itself does not give the player a full understanding of the story. There is rather a lot to it, in the end, slyly hidden in the details.
Eggs Benedict, with chicken instead of ham, and a very heavy Hollandaise sauce. Plate decorated with enough fruit garnishing to make a fruit salad. Choice of coffees (filtered or percolated) to finish.