With Pulitzer Prize-winning source material and an accomplished cast, Ewan McGregor’s directorial debut, “American Pastoral,” had to work hard to overcome its advantages but, in miscasting himself as the lead, McGregor succeeds in failing. Philip Roth’s 1997 novel about a successful family man undone by the tumultuous 1960s is adapted into a weirdly inert melodrama, and I hate to say it, but McGregor’s performance sticks out as the worst part.

The novel is framed in a flashback. Nathan Zuckerman, a character Roth frequently employs, attends his 45th high school reunion and ponders a veritable shrine to star high school athlete “Swede” Levov (McGregor). Conveniently, Swede’s brother walks up to fill Zuckerman in on the decades of despair and ruin that befell his locally renowned brother before his recent demise. From there, we are told Swede’s story.

Readers no doubt savored brilliantly written scenes with Roth surrogate Zuckerman, but for the purposes of the film, this was totally unnecessary and further emphasizes McGregor’s estrangement from Roth’s fictional world. As Zuckerman, actor David Strathairn makes sense as a Jewish intellectual. To then see McGregor as a man whose Jewishness is an important part of the character and story is simply confusing and certainly unconvincing.

The sad story of “Swede” Levov coincides with the United States’ painful military involvement in Vietnam. Levov marries a gorgeous former Miss America contestant (Jennifer Connelly), and they have a lovely, headstrong daughter named Merry who suffers from a significant stutter. I know this is part of the book, but anytime an actor, in this case Dakota Fanning, gets some kind of impediment like this, I can just see them licking their chops for a juicy onscreen affliction to portray. It’s instant character.

As a child, Merry is taken to an astute therapist who thinks the stutter is repressed resentment against her parents, especially her mother. As Merry grows up, her resentment becomes distinctly unrepressed, taking the form of bitter and outspoken protest against the Vietnam War.

When a post office is bombed and someone is killed, Merry goes missing and is widely suspected to be the perpetrator. Swede spends the next five years searching for his daughter, taunted with clues from one of her New York City friends, who extorts money from him, psychologically torturing him and eluding him.

Swede’s heartbreaking search for his daughter, who may very well be a murderer, tears him and his marriage apart, and lifts the veil of respectability from people and society all around him. It is an interesting story, but this adaptation is strictly by the book.

Characters often seem to be reading aloud from the novel itself, as if we were witnessing a costumed audio book. To match the verve of a Philip Roth book is a tall order, and McGregor is not up to it.

There are plenty of good scenes, but ultimately “American Pastoral” is less than the sum of its admirable parts. The story is meant to capture an American event through one man’s misadventures, but the overall effect is of a painful melodrama, not a powerful drama.

“American Pastoral” is currently available to rent.