I was in a room with Martin Scorsese once. It was a private audience, arranged by the Museum of the Moving Image, with a small group of film critics. We were free to ask him anything we liked. I’ll just admit it: I was too intimidated.

Not physically, although Scorsese did grow up around the kind of violence that would become his hallmark in gangster films like GoodFellas, Casino and The Departed. No, the intimidation was entirely intellectual: I couldn’t keep up. Scorsese is not only a famously fast talker — really fast, like the “legal” guy in a car commercial — he is also prodigiously, monumentally knowledgeable about movies. Talking to Scorsese is a bit like trying to return Andy Roddick’s serve, or going jogging with Usain Bolt. Most of us couldn’t do it even with years of training.

Richard Schickel, however, does have the training, and he puts it to good use in his new book, Conversations With Scorsese. A longtime film critic, first at Life magazine and then at Time, Schickel is one of the few with the expertise, mental acuity and sheer stamina to undertake this project. The book’s very title — conversations, plural! — is impressive.

Schickel has some important qualifications. For one, he has watched the director’s career unfold in real time, from his 1967 feature debut, Who’s That Knocking at My Door to the 1980 masterpiece Raging Bull to last year’s tepidly received Shutter Island. Schickel is also a fellow filmmaker, mostly of documentaries; his 2004 film, Scorsese on Scorsese, led to this book. And at 78, the author is a decade older than his subject, giving him some gravitas, but also many shared cultural reference points.

Conversations With Scorsese has a chatty, collegial feel, though Schickel does his best to focus the discussion and nudge Scorsese toward introspection — both difficult tasks. Chapter by chapter, the book tackles Scorsese’s major feature films, documentaries and even his short film, Life Lessons (part of a mostly forgotten 1989 shorts anthology, New York Stories). What emerges, between digressions and tangents, is a portrait of a self-made artist, an insecure outsider and an inveterate obsessive whose passion for movies — making them and watching them — may be unrivaled.

Some of this ground has been covered. Scorsese insists, as he has for years, that his films do not glorify violence, but express the fear he felt growing up on a Lower East Side ruled by Italian-American dynasties. More surprising is that Scorsese was actually ashamed of his background (most people would brag about it) until Raging Bull, which served as his coming out. “I didn’t care anymore in terms of being silent about where I came from,” he says of that film. “Because that world is disappearing and it’s gone now, but what remains in my memory was its atmosphere of fear.”

The book also offers clues as to why Scorsese seems critically and commercially respected yet, in some ways, little loved. (His only Oscar came for directing 2006’s The Departed.) Scorsese’s mind simply may work on too high a plane: How many viewers noticed that the climactic fight with Sugar Ray Robinson in Raging Bull was modeled on the shower scene in Psycho? Or that the changing color schemes in The Aviator tracked the changing types of color film used during the ‘40s and ‘50s? Or that there are X’s scattered throughout The Departed as a homage to the 1932 film Scarface?

Scorsese clearly prefers to discuss the professional over the personal, and Schickel is too gentlemanly to press. That’s fine when it comes to Scorsese’s brief drug use, glancingly mentioned. But what about Scorsese’s unpopular decision in 1999 to present a lifetime achievement Oscar to his hero, Elia Kazan, still regarded by some as a traitor who cooperated with McCarthy’s communist-hunting regime? It’s a fair question for Scorsese, whose films are steeped in themes of loyalty and betrayal. But whether by agreement or accident it never comes up, and it’s a glaring omission.

Still, Conversations With Scorsese is a valuable document. What Google did for the world’s books, Schickel has done for Scorsese’s brain, and both men should be thanked for it. Schickel may also be the only person who has ever mentioned a movie to Martin Scorsese — in this case, Central Airport, from 1933 — and gotten this response: “Oh, really? I haven’t seen that.”