I find it interesting that many people find the ending of the book frustratingly obscure or deliberately ambivalent. (Caution: Spoilers ahead.) The Times review says:
And in "The Magus," the story of a young Englishman who gets caught up in the frightening dramatic fantasies of a strangely powerful man on an Aegean island, he again wrote an ending of self-conscious ambiguity, leaving the hero's future an open puzzle that readers are challenged to solve for themselves.Well, as much as one hates to disagree with the New York Times, I did not find the ending all that ambiguous. In terms of plot (though not of metaphysics or of morals) the biggest question is: Will Nicholas and Allison get back together? When they meet, at the end of the book, that is the issue before them. Although no explicit resolution is given, Fowles gives a rather broad hint, by ending with a famous quote from an ancient Latin poem, the Perevigilium Veneris:
cras amet qui numquam amavit
quique amavit cras amet
I would translate this, rather literally, as "tomorrow let him love who never yet loved / and may whoever has loved love again tomorrow." The Loeb edition has "To-morrow shall be love for the loveless, and for the lover tomorrow shall be love." Finally, Eugene Ehrlich in Amo Amas Amat and More, translates as follows:
May he love tomorrow who has never loved before;
And may he who has loved, love tomorrow as well.
In terms of the plot, this seems pretty clear to me. "The one who has never loved" is Nicholas, who is basically a selfish jerk, who, by the end of the novel, is learning what it means to love; while "the one who has loved" (quique amavit) is Allison, who (with all her many faults) has loved Nicholas better than he deserved. Surely the implication is that they both will finally find mutual love and together have a future (cras)?
Have people found the resolution ambiguous because they were unable to read Latin? In fact, in the foreword to the revised edition of The Magus, Fowles suggests as much, saying that the "general intent [of the ending] has never seemed to me as obscure as some readers have evidently found it — perhaps because they have not given due weight to the two lines from the Perevigilium Veneris that close the book ..."
In my opinion, then, the "deliberate ambiguity" is just not there (or is less than usually supposed), and this leads me to see Fowles as a somewhat more traditional storyteller (at least in this case) than others saw him, and perhaps than he saw himself. But it is clear, in any case, that the world has lost a thoughtful and thought-provoking artist.