by John Updike, Knopf, $17.95. S. by John Updike. Knopf, $17.95. Mr. Updike’s latest novel is an acid comedy of illusions and delusions told entirely in the words of a woman who is both deceived and deceiver. Sara is that currently fashionable heroine, the middle-aged matron who flees luxury and a boring husband to find freedom or her true self or, in Sara’s case, Spiritual enlightenment at an ashram somewhere in Arizona. Liberation from the gross material world is what she has in mind, but as a proper New Englander she pursues that goal with moderation. She stows her family silver out of her husband’s reach and does not overlook the joint bank account. Mr. Updike has been ingenious and amusing in revealing the actuality of the ashram through the enthusiastic hurblings of a newcomer who does not understand what is going on around her, and he has evidently enjoyed boning up on Oriental mysticism. He has even provided a glossary, from abhayamudra to yuganaddha, for readers afflicted with avidya. What he has not provided is any convincing reason to consider Sara a modern equivalent of Hester Prynne, of the Scarlet Letter, although he certainly wishes her to be seen in that character. Now, why should Mr. Updike cling to Hawthorne’s coattails?