Both TOatEotL and The Graveyard Book both have serious reflections of A Wrinkle in Time.
Anyway, I read Ocean about three years ago... and loved it. Of the four of Gaiman's works that I've read, it really stirred up great feelings. Nostalgia, innocence, friendship, fears of the unknown, helplessness, loss of innocence, unintended consequences, affection, adoration, commitment, promises, broken promises, forgetfulness, and the passage of time are all used by Gaiman to lead me to my own feelings from the past.
Spoiler Alert!!!
My book club read it... and many views of the actual events of the book emerged.
I thought it was fairly straight forward that the narrator related the facts as reality. The supernatural Hempstocks and the supernatural evils in the narrative are real. The narrator's forgetfulness was the Hempstock's gift to him... although his love and guilt towards Lettie kept trying to resurface.
Others thought it was all a mental construction of a child to deal with his attempted murder by his own father. The supernatural nanny, her evil scheme, and the Hempstocks were not real at all. They were just the mental projections of the narrator to alleviate his own grief.
One person thought the main story was the drowning of Lettie Hempstock. The father's anger, the nanny, and all of the supernatural elements were only psychological devices by the narrator to assuage his guilt over his part in her accident.
I think that the story is about Gaiman's exploration of the supernatural. I think he is profoundly affected by the works of Madeleine L'Engle and C.S. Lewis (and probably other authors whose writings I've not read).
I am not intending this to be an essay on psychology versus theology. I just want to say that I thought the story telling was excellently open ended to allow for a number of personal interpretations.
When I was a theological grad student, I learned about the terms exegesis and eisegesis. These terms come from ancient Greek and refer to "leading out" (exegesis) and "leading in" (eisegesis). For reading the Bible, historical writings, and technical documents it is important to use exegesis.... to let the text speak for itself... to let the words in their own context dictate the meaning.... to let the text 'lead out' for human understanding. When reading fiction or other writings where the interpretation can be open to the reader, then we use eisegesis.... to let our biases, our predjudices, our experiences, and preconceptions inform our understanding of the meaning.... to 'lead in' to the text. That being said, I thought Gaiman did a phenomenal job of allowing the readers of my book club to each eisegete Ocean. I feel that most writers cannot achieve a concern in their readers to want to perform eisegesis because they don't care for the characters, the situation, nor the story enough to do so. I have read books that I have been invited to eisegete the story, yet have not cared to do so.
Gaiman masterfully made me care and still left it open to interpretation. Brilliant.