Eric Idle turned up at the 92nd St Y the other night to talk about some projects coming to fruition, including the imminent, fanatically awaited Broadway opening of “Spamalot.” Mr. Idle, one-sixth of Monty Python, began with a series of comic riffs, a kind of compact stand-up routine. A host then joined him for what was shaping up to be a sometimes desultory, sometimes funny, extremely hagiographical Q&A. One question led Mr. Idle to recall the stunned silence that greeted the Pythons when they first performed on American television. He was sympathetic to the befuddled Yankees: How could they hope to make sense of – and here he switched to the voice of a Pepperpot, the squawking British biddies forever turning up in the “Flying Circus” – some nonsense about burying a cat?

The effect was astonishing, as if someone had popped open the building’s sunroof. The audience fell into hysterics. So did the interviewer, who couldn’t quite manage the next question. So did Mr. Idle. Was it because that high, goofy voice triggered a thousand other memories of inspired Python lunacy? Or was the Pepperpot herself so spectacularly funny that even an indifferent audience would have burst out laughing?

In 2003, Mr. Idle spent three months performing a stage show across North America. His show combined new material with old Python favorites like “The Lumberjack Song” and “I Like Chinese.” On the eve of “Spamalot” (probably no coincidence), a journal he kept throughout the trip has been published in book form. “The Greedy Bastard Tour Diary,” like the 15,000-mile voyage it records, can be long and repetitive. Mr. Idle has a sharper eye for portraits (like the PR man who “battles along like a cross between Max Wall and Shakespeare’s cheerful Richard the Third”) than for landscapes (e.g. the “intense golden blush of dawn in a pale green sky” over Las Vegas, among many other florid descriptions). But it has its laughs, and its insights, not least about the mysteries of Monty Python that were captured by the sudden, disruptive appearance of the Pepperpot in Buttenwieser Hall.

When Mr. Idle says “tour diary” he’s not kidding. The book is based on entries he posted daily at Pythonline, the group’s Internet home. He devotes a short chapter to each of the trip’s 80 days, not counting a chapter for intermission and an epilogue to puff for “Spamalot.” His voyage began in the East and would lead him, like Odysseus, home to his wife in Los Angeles. Mr. Idle had toured before, with the Pythons and on his own, but this would be different. For one thing, an ankle injury forced him to spend the trip trying out his own silly walk. Also he planned to do stand-up for the first time, an anxious-making development. It helped to have pals like Eddie Izzard around to offer some pointers.

Stories here about life on the bus, and Mr. Idle’s dehumanizing, wall-to-wall interview schedule will be familiar – probably too familiar – to readers at all acquainted with the lives of actors, rock stars, and presidential candidates. The minutiae of shaping the show will likewise titillate few beyond the ranks of die-hard fans and stage managers. (“We now run 55 minutes for act one and 46 for act two,” runs a diligent report after some trimming in Rutland, Vt.) Yet Mr. Idle manages, around the edges, to turn this into a personal book, a kind of free-floating memoir.

Mr. Idle touches on the death of his father in World War II and the harrowing childhood he spent at a dismal boarding school, but is more poignant about his grown-up interactions. When he met George Harrison, he writes, “It was love at first sight. . . . We’d stay up all night playing and laughing. He made me do all the Python sketches and I made him do all the Beatles songs.” Harrison famously put up the money for “The Life of Brian” just because he wanted to see the film. Throughout the tour, Mr. Idle kept an “encore bucket” at the edge of the stage. If the audience liked the show and expected an extra number at the end, he told them, they ought to pay for it. More than a few women parted with their panties, which Mr. Idle records as the peak of his entire career. The money, but not the underwear, was donated to Harrison’s favorite charity.

The other Pythons hover throughout the book, as they must have throughout the trip. He seems to regard Mr. Cleese with a measure of awe, and toys with people who can’t keep their Pythons straight: “Whenever I’m mistaken for Michael Palin, I always say, ‘Yes I am him. Now f— off, you ugly old bastard!’ Because I want to help destroy his reputation for niceness.” But Mr. Idle can also grow unexpectedly melancholy about “the semilegendary snake” now and then. “Being an ex-Python is weird,” he writes, in an incisive, honest passage:

Those young men are long since gone. We have to talk about them as though we still are them, but we’re not, you know. They were smart, young, and terribly clever. We older, wider, and grayer men are their descendants. I used to be Eric Idle in Monty Python. But now I’m not. …I think that’s why certain interviews are so taxing for me: they only want to talk to him. And I’m not him, any more than Ringo is still Ringo.

It’s more complicated than even that, of course, as Mr. Idle well knows. Near the end of the tour he writes that he has made himself a true comedian instead of a mere comic actor, able to entertain a crowd alone, in his own voice. “Of course I am lucky,” he acknowledges. “I don’t come on alone. I have the ghosts of the Pythons with me, and the audience is already alive and warm and welcoming and buzzing with expectation, and yes I do get a huge greeting, which I now shamelessly milk, but I still have to make them laugh.”

Sometimes Mr. Idle manages to do this by putting an odd observation just right. “All religions seem to dislike breasts, but it’s just the opposite with me,” he writes. Surprisingly often the comedy is pedestrian, domestic: “My favorite position is the Male Marital Position: flat on your back with your wallet wide open.”

I happened to read this book while looking over some Python collections I had memorized as a kid – a warm-up for “Spamalot.” Even now, they’re not just brilliantly funny, they’re hilariously strange. After revisiting the Dead Parrot, Nudge Nudge, Argument Clinic, and a hundred other ingeniously oddball sketches, the ordinary laughs of Mr. Idle’s book seem ordinary, normal. The disappointment doesn’t come from discovering that Mr. Idle has clay feet (he doesn’t), but from finding that a Python has feet at all, and not a mermaid’s tail, or a pair of sleeping bricks, or a Pepperpot’s sensible flats.