Judd Apatow likes to keep stuff. He even goes as far as to say he’s a hoarder. But unlike a regular hoarder, he insists all the things he keeps are awesome — and neatly collected.

“I save everything, but I don’t have it in a mound in the middle of the house,” the writer-director says. “I’m the Felix Unger of hoarding. Everything is taken care of very well.”

Fans of Apatow — and fans of comedy in general — get the benefit of this personality quirk with the Tuesday publication of “Comedy Nerd,” a bulging, 570-page, photo-filled memoir from every chapter of his storied career.

It’s packed with behind-the-scenes snapshots from sets, script fragments, notes from network bosses, essays, movie posters and miniprofiles of his fellow comedians. There’s his late-night ideas for “Knocked Up” typed into a BlackBerry and a photo of Adam Sandler’s old fake ID.

“I feel like just making this book justifies the hoarding,” Apatow says with a laugh. “I did save it for a reason. I wasn’t wrong to not throw out my photograph of Billie Jean King from when I was 10 years old.”

The producer, director and writer behind the movies “This is 40” and “The 40-Year-Old-Virgin,” was inspired to make the book from similar memorabilia-filled offerings from the Marx Brothers and “Saturday Night Live.”

He spent a year going through his photos — 400,000 of them — keepsakes and clippings, then scanned everything into his computer and laid out the entire book in a raw way. He spent the next year writing essays and captions.

“The idea was that the experience of looking at the book would be as if I was over your shoulder explaining what things were and telling you stories,” he says.

Apatow includes memos he got from network standards — “Just a reminder that Ben’s gyrating dance not be sexual,” one reads about “The Ben Stiller Show” — as well as Garry Shandling’s note-filled revision to a script from “The Larry Sanders Show” and a page from an unproduced screenplay written by Owen Wilson. Apatow reveals Paul Rudd had a pretty funny but lost cameo from “Bridesmaids.”

He includes the increasingly snarky email exchanges in 2001 between him and writer Mark Brazill beefing over a long forgotten comedy sketch, and there’s an alternate initial setup for “Anchorman” — a group of anchors on a plane crash into a snowy mountain that becomes a parody of the movie “Alive.”

Apatow is even not afraid to show times where he was foolish. “I think a lot about all the people I got a chance to collaborate with and how magical a bunch of those times were. So I’m very happy to also show where I was an idiot or awful because that is part of the journey,” he says.

There are pages dedicated to TV shows that never got made, like “North Hollywood,” about three friends trying to break into show business that would have starred Amy Poehler, Kevin Hart, Jason Segel, January Jones and Judge Reinhold.

It seemed fun, at least judging from the photos at a party during the shooting of the pilot that shows folks getting stoned. “Do people want me to show the photos of them smoking enormous joints in the year 2002?” asks Apatow. The answer is yes.

Failures litter the pages of “Comedy Nerd” despite the author’s bankable instincts, which have given us “Freaks and Geeks” and “Girls” on TV and the Oscar-nominated films “Bridesmaids” and “The Big Sick.”

“The hard part about comedy is it’s always an experiment. And everybody has a completely different opinion about how the story should be told and what’s working and what not working,” he says.

“So a lot of having a career in this business is learning how to have those conversations that I didn’t do well. For many years, I got very emotional and resistant. It led to a lot of cancellations.”