When Patti Davis' book goes into paperback, she ought to add another chapter about what happens to the daughter of a president when she writes a novel about her family and goes on a book tour.

The past few weeks have provided a perfect epilogue for "Home Front," the tale of Beth Canfield, a girl who would rather not be the daughter of a governor on his way to the White House. Beth keeps trying to be the leading character in her own life and keeps ending up a subplot in her father's.

It was like that in Patti's real life. It's like that in the book Davis has written about her life. And it's like that in the book tour about the book about her life.

The escapades of Beth's youth are fairly tame -- one lover, a marijuana joint or two, a stint as an anti-Vietnam War activist. So, for that mattr, were the "rebellions" of Patti's youth. In her own words, "I mean, I considered myself fairly normal, I didn't, like, burn out on acid or something." But in and out of print, as Patti or Beth, her behavior and beliefs were judged by one standard. As Harriet Canfield, in the role of Nancy, says, "I don't know how you can do this to your father."

The author, now 33, is clear-sighted enough to know this, and to know what she was getting into when she got into print. The novel she has written is not illiterate and not literature. It is interesting -- interesting only -- when she is writing about her parents.

The image of a daughter struggling to make contact with a Teflon-coated father has touching moments: "I felt that nothing I said made an impression on him -- that my efforts were wasted. Each time my hopes were raised that I might be able to reach him, that he might understand what was in my heart, but each time I came away deflated, feeling more distant from him than ever."

The troubles her character has with a mother who can see her daughter's quest only as a threat are sadly believable: "All I'm asking," says this mother, "is that you keep your father in mind when you choose your friends and your activities. Think of how it reflects on him. Is that too much to ask?"

There must have been a catharsis in writing these lines out of her life. But she couldn't write the dilemma away. Indeed, in some ways publication proved her point.

Friends of her father criticized the book. Enemies of her father reveled in its prickliest moments. A slew of talk shows invited Patti because of her parents. At least two -- Merv Griffin and Joan Rivers -- disinvited Patti because of her parents. She was always seen as a daughter rather than an author. Even her parents reacted to the novel in character: Her father behaved with chipper, benign denial -- "interesting fiction" -- and her mother with hurt at a "hostile" act.

But this is not a Poor Patti column. There are "children" who handle reflected fame with more ease and more grace than Patti. Even Ron Jr. There is, however, a particular problem for the son or daughter who loves and yet also disagrees with a very public parent. You can trace the struggle and the yearning in Beth's relationship with her father: "I was doing what I felt was right. So was he. And between those two realities was only distance."

Patti Davis is antinuclear while her parents are pro; she is pro-choice while her parents are anti; she is jeans while they are couture, and nontraditional while they are highly traditional. She will not even say whether she voted for her father. It must have been, must still be, difficult for such a daughter to know when she is following her conscience and when she is just rebelling, to speak her mind when it will be used against someone she clearly loves, to find her "self."

This was an attempt to write her own story, to control it, but it didn't work. Even Patti's prime time in the media spotlight is played out in her father's shadow. I don't know when Patti Davis will shake free of being president's daughter, but I have a good guess. It's January 1989.