You remember Sophie's World, last year's runaway success? Written by a Norwegian high-school teacher and novelist, it purported to make the Great Questions of philosophy accessible for the pre-teens. The Solitaire Mystery ploughs the same furrow and what an arid one it is.
This genre of writing aims to give complex ideas the gloss of the moment.In this case Paul Daniels and Baudrillard (father of post-Modernism) hop TV channels with Bettelheim and the Brothers Grimm.
So we have a child and his alcoholic father searching for his "real" mother, who has lost her Self in becoming a model, intercut with a magical world of fairy tales in the mittel-European woods. Both the magical story and the drunken father's ramblings bang on about the relationship between the human and divine, epistemology, existence, essence and attributes.
Neither any hint of characterisation nor any desire to make interesting prose impedes the author's pedagogic progress through the nature of reality. As Jostein Gaarder's writing style is, to put it mildly, deathly dull, those wishing to inoculate their children against curiosity in ideas should buy the book.
Others should invest in Lewis Carroll who did this sort of thing much better a century ago. Older students could go for Bertrand Russell's History of Western Philosophy. It cannot be savoured in one gulp but will mature on the shelves with the reader, unlike The Solitaire Mystery, which will rapidly go mouldy before your eyes.