TELEGRAMS IN FRANCE are blue and written in longhand. Bob Dylan's real name is Zimmerman. LAX is the code for Los Angeles International Airport.

Devotees of fact will not mind that some of the information provided in William Wharton's Dad is familiar. A refresher course in cardiopulmonary resuscitation is useful, and who would know the varieties of male catheter? R. D. Laing's theory of schizophrenia, the Leboyer method of childbirth, the Coriolis effect (which determines the swirl of water down your bathtub drain) -- yes.

Devotees of feeling, too, will find themselves in a richly cultured medium. If anything, Wharton is even more patient in his observation, even more particular in his reporting, of the inner life than of the outer. He is loyal to his data as any Coriolis, Leboyer or Laing: umimpressed by the grand, unsurprised by the strange, unashamed of the trivial, never bored by the repetitious.

It's amazing that this obsessive, nose-to-the-ground method succeeds as well as if frequently does. Wharton writes with apparent artlessness; he must be one of the least quotable writers. He works not with jewels but with mud. And yet he raises -- not, as one would like to write, "before we know it," but eventually, eventually -- a kind of temple. His faith in his story, whether always merited or not, is always palpable, and that's meritorious.

The plot of DAD is so simple that most of it may honorably be told. Its central character is John Tremont, a 52-year-old artist who has returned from France following his mother's heart attack in Los Angeles. He is forced to remain in L.A. when his father suffers a peculiar mental collapse.

Tremont eventually learns that the old man has been leading a secret second life -- all in his mind, apparently, despite some speculation about a time warp. This second life strangely resembles his real one, but is taking place in Cape May, New Jersey, and is entirely happy. His Cape May wife is Bess, a younger, idealized version of his shrewish Bette, who torments him in L.A.

The bulk of the novel is John Tremont's story of trying to save his father from madness and death. Finally he can stay no longer, and sets out with his son Billy, 19, to drive across America and then fly home to France. The Los Angeles portion is broken into sections, interspersed with sections of the cross-country trip; the latter are narrated by Billy.

Long passages work magnificently. In one, Tremont has taken his disoriented father home from the hospital and is trying to rehabilitate him. To this exhausting work he brings a devotion resembling, one feels the author's devotion to the novel itself. He must feed and dress his father, wrestle him out of closets and out from under beds, wash feces from his skin and hair. Because we're emotionally involved, power accumulates with accumulating detail.

Too often, though, we aren't made to care; and when that's the case the accumulation of detail, atomized and itemized, can make us feel bound beneath a dripping tap.

The leaping back and forth in time and space -- as we shift between the viewpoints of Tremont and Billy -- doesn't work either. Billy is too unimportant, and so is the cross-country trip he narrates. The real story takes place in L.A. The marriage of these unequal stories is forced and unhappy, a matter of imposed design, arising from no narrative necessity.

Readers of Wharton's spectacular first novel, Birdy, may be surprised at how much in Dad seems familiar. Here again we have two first-person narrators, taking turns as storyteller, though without the same logical necessity for such a device.

And here again we have Birdy's central plot: one character is caught in a fantasy detailed to the cuticles, a fantasy so absorbing that he loses his mind, personality, everything. The other character tries to save him, bring him back.

Unfortunately, the fantasy of living in Cape May, New Jersey, is less intriguing than the fantasy of thinking you're a canary, and therein lies a large part of DAD's inferiority to Birdy. Wharton assumed a dangerous risk in writing a second novel (one feels, actually, that it must have written first) that so often invites comparison to its predecessor. They are so plainly sisters, and one the less lovely, less charming, less clever. To the reader of Birdy, DAD will seem a little stale; and so, sadly, will Birdy now seem, whose freshness once was stunning.

Birdy will remain, deserves to remain, a landmark novel of recent years. But some of the features it shares with Dad will now be seen as parts of the author, not parts of the book -- which is excellent for literary biography, but a fractional undoing of fiction.

Well, old books change when we read new ones. Just as life dies into art, art dies, continually, into life. Though this somehow always surprises us, it shouldn't: "The past," as T. S. Eliot wrote, "[is] altered by the present as much as the present is directed by the past."