Most of the chapters in Colin Jost’s memoir, “A Very Punchable Face,” open with a pair of complementary quotations, whose sources run the gamut from Tennessee Williams and Franz Kafka to Robin Williams and “an insane woman on the subway.”

But midway through the book, one essay begins instead with a note from Jost, advising a host of potential readers — his parents, grandparents and fiancee, Scarlett Johansson, among them — to consider skipping it. The ensuing chapter turns out to be a meticulously compiled recollection of instances in which the “Saturday Night Live” head writer has lost control of his bowels in sidesplitting fashion.

“The chapter about how many times I pooped my pants was pretty enjoyable,” Jost says. “That was cathartic. And the sad thing is that as soon as I finished the book, I also remembered several other stories that are harrowing about this subject. So that’s one chapter for book two.”

Jost, 38, approaches “A Very Punchable Face” with his characteristically matter-of-fact tone and self-effacing persona, rattling off amusing anecdotes from an uncannily eventful existence. There’s the time he wrote a front-page story for his hometown Staten Island newspaper about paramedics administering CPR to a raccoon. More recently, Jost recalls a trip to Nicaragua that left him with botfly eggs embedded in his legs.

He also opens up on the frenzied comedy culture at SNL, where the Harvard product has risen to head writer and Weekend Update co-host — but not without a healthy dose of demoralizing doubt along the way. And Jost acknowledges that, after a decade and a half at 30 Rockefeller Plaza, the sketch comedy mecca won’t be his home for much longer.

Q: This book leans into self-deprecation, starting with the title. How did you land on the name?

A: Well, multiple friends have told me that I have a very punchable face. Then there were so many stories already about me getting injured or humiliated that the title actually helped organize the book a little bit around that theme. As I was finishing the book, I realized that on SNL the audience just loves when I get physically hurt, or even if I seem emotionally fragile. If I make a joke about a bad relationship with my dad, the audience really laughs — and I’m like: “What’s going on guys? Why is that so funny?” But people enjoy seeing me suffer, and I get it.

There was a rhythm to the book’s storytelling that reminded me of stand-up comedy. How did your stand-up experience inform the way you went about putting together this memoir?

That’s an interesting observation. I didn’t really think about it that way, but I wanted to write it pretty naturally, in what I think my voice is, and to make it conversational. I never wanted to feel like I was switching into some arch writing style. But, yes, I think the storytelling part of stand-up helped me a lot because you start feeling what the rhythm of a story is. There is a repetition in stand-up — you feel what part you should cut, what part you can spend more time on — and that’s what the [book] editing process is like. But your only audience is yourself, which is a very strange thing. You’re in your head a lot more.

Is there anything in the book that you hesitated to include because of how certain people or, perhaps, certain corporations might react?

[He laughs.] Honestly, I don’t know. I didn’t show it to [SNL creator] Lorne [Michaels], and I didn’t show it to NBC or anything. I try to be fair about everything, so I’m not a person who ever comes from a place of wanting to be mean or get people in trouble. I don’t know if there are corporate things or things about censorship on the show that I’m writing about, or things about Trump hosting [in November 2015]. I don’t really know if NBC will have objections. So I guess we’ll see.

The chapter “Why I Love My Mom” documents your mother’s harrowing experience responding to 9/11, as chief medical officer of the New York City Fire Department. How did you get into the head space to revisit that time?

That was definitely, by far, the hardest chapter to write, and also to reread anytime I had to go back to it. I wanted to tell the story in a way that did justice to my mom, and in a way that showed her heroism [on 9/11] and also her everyday heroism. It was really emotional. So many of the people that died around my mom were dear friends of hers, and also people that were in my life. The people she worked with were her family. We went on trips together, and I went to every fire department retreat that they did or barbecue that people had. I remember this moment where 20 close friends of my mom essentially disappeared overnight. That’s a delicate thing to write about, and I just wanted to kind of let the story tell itself.

How has your mother reacted to the memoir?

In general, she was very happy she didn’t know so many of these things were going on before she read the book — not about that chapter, but about the other incidents in my life. She was like, “I can’t believe how many things I would have been horrified by if I knew they were going on.”

In the final chapter, you reveal you’re “preparing mentally to leave SNL in the near future.” What made this the right platform to share that news?

It just felt right as I was writing. I think what I wanted to open up about was just that fear of leaving and the fear of letting go of something that has been so important in my life. It’s scary thinking about leaving. I guess, on some level, I needed to face that or think about it, and that’s how I ended up there. It wasn’t really with a specific date in mind or a timeline in mind. It really was the emotional process of thinking about it.

Thomas Floyd is a multiplatform editor who writes about arts and entertainment for The Washington Post.

A VERY PUNCHABLE FACE

By Colin Jost

Crown. 336 pp. $27