Seeking to delineate the limits of crime, mystery and thriller fiction using these stories’ manifest commonalities only sounds like a simple endeavor. In fact, it’s as difficult and frustrating as trying to put together a perfect list of must-read books from the genre. Every time you think you’ve satisfied all possible criteria, some additional work challenges your descriptive boundaries.

Ask yourself this: Why is it that the novels of Raymond Chandler, Dashiell Hammett, Dorothy L. Sayers, Jo Nesbø and Sue Grafton are automatically shelved in bookshops under Crime Fiction, yet other no-less-compelling tales of mayhem and mystery—such as Wilkie Collins’ The Woman in White (1860), Harper Lee’s To Kill a Mockingbird (1960) and Fyodor Dostoyevsky’s Crime and Punishment (1866)—usually find homes in General Fiction? That last book’s absence from the crime department is particularly puzzling, since Dostoyevsky’s story is all about a brutal slaying in St. Petersburg, Russia, and the perpetrator’s efforts to conceal his transgression. Crime and Punishment even sends a detective after its murderer, one Porfiry Petrovich—who is known to have been a model for television’s Lieutenant Columbo, and earlier this decade was recruited to star in a mystery series by R.N. Morris.

Did you read the Rap Sheet’s review of ‘Die a Stranger,’ by Steve Hamilton?

Clearly, the definition of “crime fiction” is rather less than rigid. The late British author and scholar H.R.F. Keating characterized it simply as “fiction written primarily for its entertainment value which has as its subject some form of crime.”

Stephen Booth, who pens a fine police-procedural series set in England’s scenic Peak District, said something similar a few years back. He applauded the genre for allowing authors “tremendous freedom to write about any subject we’re interested in, while maintaining a narrative drive and making it entertaining for the reader.”

But that elasticity and freedom have also made it tricky to unify the breadth of modern crime, mystery and thriller fiction beneath a single standard.

Kate Atkinson, for instance, has produced four books featuring ex-cop, ex-husband and present-day private investigator Jackson Brodie, most recently Started Early, Took My Dog (2010). Adapted by the UK’s BBC One as a mini-series, they’re unmistakably works of crime and detection. Yet they’re almost invariably catalogued as General Fiction, presumably because Atkinson wrote several mainstream novels (beginning with 1995’s Behind the Scenes at the Museum) prior to introducing the Brodie tales—and booksellers don’t much like dividing an author’s output into separate categories, since it complicates finding the titles later on.

Conversely, Megan Abbott made her bones composing such memorable stories of historical malfeasance as The Song Is You (2006) and Bury Me Deep (2009). Her 2011 novel, The End of Everything, was really more about young girls discovering the shadowy depths of the adult world than it was a yarn about unlawful doings. Still, it winds up being slotted in Crime Fiction along with the rest of her work.

The nuisance of trying to establish bright lines between what is and is not crime fiction becomes especially pronounced when we move into the subgenre of thrillers—narratives that claim suspense, tension and exhilaration as their principal ingredients.

As an example, why are Harlan Coben’s tight-twisted tales filed alternately in bookstores as Crime Fiction and General Fiction? You could ask that same question about Philip Kerr’s oft-brilliant Bernie Gunther novels, Mark Mills’ historical espionage adventures (the newest of which is House of the Hunted), or William Landay’s works of legal suspense (such as Defending Jacob). And why wouldn’t you ask it of Stephen King’s 11/22/63, in which a young man’s leap back through time may give him the opportunity to prevent President John F. Kennedy’s assassination? 11/22/63 is arguably speculative fiction, yet it was recently awarded Best Hardcover Novel of the Year honors by the International Thriller Writers association.

Talk about confusion of classifications!

All of which brings us to a new volume that tests the bounds of crime fiction: Stephen L. Carter’s The Impeachment of Abraham Lincoln.

This story offers a classic “what-if” scenario. In its alternative construction of history, Abraham Lincoln, the 16^th president of the United States, doesn’t die in April 1865 after being shot in the back of the head by renowned actor and Confederate sympathizer John Wilkes Booth. Instead, Lincoln survives, while on the same night Vice President Andrew Johnson (who in reality succeeded Honest Abe) is assassinated by a Booth co-conspirator, and another wounds Secretary of State William Seward so severely, the diplomat retreats from public view. (Actually, Seward recovered from his wounds and went on to engineer the U.S. purchase of Alaska from Russia.)

Two years after Booth’s assault, and following the death (by suicide?) of the president’s wife, Lincoln’s growing contingent of enemies—led by radicals within his own Republican Party, who believe the post-Civil War South deserves much harsher treatment than it has received—endeavor to oust him from the Executive Mansion. They charge Lincoln with, among other offenses, acting the role of “a petty tyrant” and trying to usurp congressional authority by establishing military rule in what was then known as Washington City, “with himself at the head.”

If this tale focused exclusively on congressional hearings to impeach and remove Lincoln from office (which the author has based, in part, on the actual impeachment and trial of President Johnson in 1868), it might easily be classified as mainstream fiction. But Carter—a Yale law professor and the author of four previous legal/political thrillers, including The Emperor of Ocean Park (2002)—layers beneath his courtroom drama a multifaceted and dynamic subplot involving the murder of one of Lincoln’s attorneys (supposedly in company with a prostitute), coded messages that could reveal a “conspiracy [that] reached the heights of the President’s closest friends and advisers,” and a packet of letters which could prove invaluable to the defense, but come from a suspect source.

Taking the lead in that subplot is Abigail Canner, a brilliant young African-American law clerk (rare in those days), who persists in yanking at the loose threads of political conspiracy long after her boss tells her to desist—only to find that her connection with those schemes is closer than she’d imagined. In addition to serving as this work’s operative sleuth, Abigail is the mirror in which we observe the class and racial struggles of mid-19^th century America, as well as the social intrigues of a capital city hinging North to South. Nearly as engaging as she are some of the genuine characters who march through Carter’s pages—everyone from the hyper-honorable Sen. Charles Sumner and the notorious Union general, politician and murderer, Dan Sickles, to a “sleepy but cunning” Lincoln.

The Impeachment of Abraham Lincoln offers us not only an American government in crisis and a capital riddled with rumor, “machination and double dealing,” but a mystery of history-changing proportions. Although its denouement features a turn that’s too convenient by half, Carter’s latest novel remains one of the finest historical thrillers I’ve read so far this year.

Just don’t expect to find it under Crime Fiction in your local bookstore.

Even though that’s exactly where it belongs.

J. Kingston Pierce is both the editor of The Rap Sheet and the senior editor of January Magazine.