The Ocean at the End of the Lane is like a surreal Pippi Longstockings as retold by a much less didactic C.S. Lewis, with Pippi taking on the role of Aslan.
The word surreal doesn't mean unreal, it means above real or greater than real. Unfortunately surreal is one of those words that has been so abused in popular use that it has lost all its meaning and now is just as a synonym for weird. All myths are surreal in the sense that they deal with things that are bigger than what is only real.
I suspect that Neil Gaiman, like so many of us that grew reading about Narnia and similar realms, probably spent his childhood expecting to walk through an old door or between two trees and find himself in the Other World. But The Ocean is not a portal quest like the Narnia books, it is an intrusion fantasy in which incredibly wonderful things and indescribably awful things intrude into our mundane world. Like all proper stories it is about wonder and fear, self-sacrifice and personal transformation. The Fantasy genre needs more stories like this that are surreal in the mythical sense, not surreal in the pointlessly weird sense.