Tim Sandlin has written comic novels about 13-year-olds and sex, about a young mother who drinks too much and misplaces her baby, about a president who dies in flagrante delicto, leaving the nation in the hands of a coke-snorting veep.

Then his father, Hoyt "Red" Sandlin, now 83, broke his shoulder. Sandlin, now 57, found himself doing a lot of waiting at his father's bedside — for information, doctor visits, medication, meals.

Sitting in the nursing home with his legal pads, he grilled the staff for salient details, many of which ended up in his seventh novel, "Jimi Hendrix Turns Eighty."

Published in January, the novel is a tragi-comic story of anarchy and aging hippies at an assisted-living facility in Half Moon Bay, Calif. The futuristic tale was described by one reviewer as a "rather disturbing" look at "old age, death, infirmity and the legacy of the 1960s."

Since America's 78 million baby boomers started turning 60 last year, dozens of novels with graying protagonists and late-life themes have hit the nation's bookstores, adding a few new wrinkles to the face of contemporary fiction and underscoring a sobering fact about readers in America: The most avid book lovers are 50 and older.

Increasingly, so are the characters they're reading about. And "the novelists are getting older" too, said Jane Friedman, president and CEO of HarperCollins Worldwide. "It's really the graying of America. ... This is not a trend. I think it's the zeitgeist."

Novels "are going to now have to have characters that the aging population recognizes," she said, and "you're going to start seeing all of those books in larger print."

A year ago, Friedman's publishing house unveiled HarperLuxe, a new line of large-print books with baby boomers in mind. And the California State Library launched "Transforming Life After 50: Public Libraries and Baby Boomers," part of a national effort to remake the country's libraries to better serve an expected wave of active, older readers.

Those readers can now encounter central characters dealing directly with the dilemmas of aging: Philip Roth's alter ego Nathan Zuckerman, 71, struggles with prostate cancer, impotence and lust in "Exit Ghost," released last month; Gina Morgan faces menopause and widowhood in Alan Cheuse's "The Fires," published in September; and George Hall, 61, tries vainly to retire in peace in Mark Haddon's "A Spot of Bother," released last year.

In other novels, protagonists in late middle age deal with elderly parents' increasing needs.

"A lot of the people writing now are in their 50s and getting to a place where they're caring for aging parents," said Betsy Burton, owner of the King's English Bookshop in Salt Lake City. "Caring for aging parents when you're facing old age yourself is a new topic."

In "Digging to America," Anne Tyler's multigenerational, multicultural, multifamily saga, grown children fret about aging parents while adopting baby girls from Korea.

In Armistead Maupin's "Michael Tolliver Lives," an aging gay man in San Francisco has to choose whose hospital bed to sit by: that of his biological mother, an evangelical Christian nearing death in Orlando, Fla., or his spiritual mother, a transsexual who had a heart attack closer to home.

And then there's Helen Knightly, the 49-year-old narrator of Alice Sebold's new novel "The Almost Moon," who has been caring for her difficult, 88-year-old mother seemingly forever. Then she stops. Abruptly.

"When all is said and done," the novel begins, "killing my mother came easily. Dementia, as it descends, has a way of revealing the core of the person affected by it. My mother's core was rotten like the brackish water at the bottom of a weeks-old vase of flowers."

Elaine Petrocelli, owner of Book Passage stores in San Francisco and Corte Madera, Calif., acknowledged that Sebold "breaks taboos" — and not just the matricidal ones.

Still, the book is "brave" and "brilliant," she said, and "anyone caring for a mother will have a very emotional reaction to it."