“Nobody dies at the end of this book,” writes Susan Morse in the preface to “The Habit,” a sometimes searing, often hilarious account of a mother-daughter relationship Hallmark probably doesn’t have a card for.

If only because there just aren’t that many people whose 85-year-old mothers decide to become Orthodox Christian nuns.

But as we enter the season when family members have more opportunities than usual to get on one another’s nerves, it doesn’t hurt to be reminded that even the people who drive us the craziest might be worth getting to know better.

Not that Morse, whose mother turns 90 two days after Thanksgiving, pretends to have the road map to happier holidays.

The youngest of four children of the late Michael von Moschzisker and his wife, Marjorie, a portrait painter, Morse found herself becoming the sibling in charge of “Operation Ma” after her father died in 1995.

“Our family is, I think, not unusual, in that people kind of spread out. Everyone spreads out and doesn’t want to have to deal with each other,” she said last week in an interview in the Philadelphia home where she and her husband, the actor David Morse (“The Green Mile,” “Treme”), have raised three children of their own.

“But when my father died, my siblings and I really kind of had to rally,” she said. “It was fun — it was really fun — getting to know the siblings more.”

And then there was Mother Brigid, as Morse’s mother came to be called after undergoing “tonsure,” a ceremony in which she became a monastic (one who, in deference to her age, doesn’t live in a religious community but whose job nevertheless is to pray).

A religious explorer (“all my life, she was hungry spiritually,” said Morse), her mother was born an Episcopalian, converted her family to Roman Catholicism for a while, and studied other beliefs after that.

“Her nature is to be an evangelist. And that was incredibly annoying. And frustrating,” Morse said. “I think Orthodox Christianity has made a world of difference to her,” encouraging her to focus on her own spiritual experience.

“There were about 12 years of real struggle with my mother and I’m not sure why this two-year period that the book is about changed everything, but I’ve tried to puzzle it out in the book,” she said.

“I think it’s a combination of that we had to see each other a lot and that we just both really needed to solve this problem that she was having.”

The problem: a bout with cancer and a fall that resulted in a broken hip and shoulder, a one-two punch all too familiar to many members of the Sandwich Generation, who’ll probably appreciate Morse’s riffs on the medical system (and in particular the acronym she used for her mother’s former HMO, derived from a phrase I can’t repeat here).

“There’s something about having a common adversary that kind of bonded us,” she said.

And when Morse, a former actress who’s worked as a book editor, realized the emails she’d been sending to update her siblings on their mother might be the basis for a book, she found a new bond.

“Everybody was saying to me, ‘Are you going to publish the book after she dies?’ I really wanted to not wait,” she said.

So she decided to share the project with her mother as she wrote it.

“I had to be introspective about her to write things about how I was feeling about her, that I had never been able to find a way to express to her one-on-one,” she said.

She’d take each chapter to her mother for review, “and I would always be quaking in my boots that she would be horrified, or insulted or just embarrassed at the idea that I was actually going to publish this thing.”

Instead, “what was so amazing (was) that I could go to her and read this stuff to her and she would be howling with laughter.”

“We had never really been able to laugh at the same joke at the same time until this book. Neither one of us really got each other’s sense of humor in a way that was all satisfying. And now we do. I feel really lucky and really grateful that we were able to do it.”