Pretty much the least interesting thing there is to know about Andrew McCarthy? He was a charter member of Hollywood’s Brat Pack.

The most interesting thing about that, meanwhile? That he ever belonged to anything. Or anyone, for that matter.

"How many things had I walked away from in my life because I hadn’t been able to commit?" McCarthy, 49, asks, not at all rhetorically, in the opening pages of "The Longest Way Home," his startlingly memoir.

Unlike fellow Brat Packer Rob Lowe’s recent nonstop dish-athon (and those of just about every other Hollywood memoirist), McCarthy doesn’t regale readers with the many juicy roles he turned down over a three-decade career and the many starlets he didn’t.

Instead, "The Longest Way Home" is a lyrical, yet unsparing account of the extraordinary lengths that McCarthy, the consummate ensemble player in such 1980s cinematic touchstones as "St. Elmo’s Fire," "Less Than Zero" and — let us all bow our heads in respect — "Weekend at Bernie’s" (I and II), went to discover and ultimately confront his commitment demons.

"I was writing the book, in a large way, to solve this sort of personal dilemma I had," McCarthy said recently by phone about the stranger-than-any-movie-plot story that begins with him getting engaged to the mother of his young daughter (he also has a son by his first marriage) and then instantly becoming a serial bolter who heads out solo to such far-flung spots as Patagonia and the Amazon. "The book isn’t really a travel book at all." Still, "The Longest Way Home" is organized as an arc of travel essays — and some very good ones at that. That’s hardly surprising given the admittedly surprising detour McCarthy’s taken off the standard issue Hollywood Thespian’s Career Map. A knack for discovering places — or new meaning in old ones — allowed him to morph into a unique working journalist/movie star hybrid about a decade ago.

Now an editor-at-large at National Geographic Traveler, his work pops up everywhere from the Atlantic to Bon Appetit and even won him the Society of American Travel Writers’ prestigious "Travel Journalist of the Year Award" in 2010.

Say what?! Blane, the preppy heartthrob from "Pretty in Pink," can just plop himself down in a snake-infested rain forest in an off-the-grid area of Costa Rica known as "the Osa" (Chapter 4 in the book)? And nobody blinks twice? "Sometimes people recognize me, and it opens doors in ways I would not be welcomed otherwise," admitted McCarthy, who seems more empathetic than your average screen idol with the rather peculiar job demands of the press corps’ ink-stained wretches.

"If I say I’m from National Geographic, people clam up or just start quoting stats," McCarthy said of those he meets while traveling. "I try not to pull out my pad and act differently around them. Instead, I run off to the bathroom a lot to write things down. People probably think I have a prostate problem!" One problem probably will never go away completely, McCarthy says: "I have that weird push-pull where I want to talk to you and not want to talk to you." Such insight wasn’t come by as easily as early fame. McCarthy unflinchingly writes about the roots of his arm’s-length relationship with happiness and personal attachments — the comfortable suburban New Jersey upbringing darkened by a distant, yet demanding father; the instant celebrity that began with a role as Jacqueline Bisset’s teen lover in "Class" and which he nearly drowned in temptations like booze over the next decade.

Still somewhat emotionally lost in his early 30s, he felt pulled to retrace a pilgrimage through Spain he’d read a book about. Somewhere along that 500-mile route of blistered feet and psyche, he writes, "my pack felt lighter ... Through travel, I began to grow up." But would he ever grow up enough to come home and finally marry "D," as he refers to his fiancee in print? That’s the through-line to the book, which McCarthy says occurred to him as he almost maniacally began lining up travel-writing assignments even as he took steps to officially settle down.

"Whenever you’re travel writing, there’s the trip you report and the parallel personal things going on that you never write about," said McCarthy, who kept two separate notebooks to force himself to do so this time. "There’s a sort of ownership that happens when you write it down. A certain solidity to what you discover about yourself when it’s not just running around in your head anymore."