Before she passed away in January, Margaret Truman had published some 30 books, including 23 mysteries, all with titles that start with the word “murder.”

Yet Truman, in her recently published last crime novel, “Murder Inside the Beltway,” still manages to develop a fresh storyline and some unusual characters.

Truman, the daughter of Harry S. Truman, is also the same Truman who started a successful singing career at 16 and was a secretary to the board of trustees of the Harry S. Truman Foundation.

But one of her more lasting legacies is a successful literary career.

In “Murder Inside the Beltway,” what starts as the investigation of a homicide of a prostitute by Washington’s Metropolitan Police Department turns out to be something bigger and linked to the highest echelons of political power.

That link is the presidential campaign of former Maryland Senator and presidential candidate Robert “Handsome Bob” Colgate and his wife, Maryland Gov. Deborah Colgate.

Sen. Colgate is a handsome, compelling man of the people seeking to unseat President Burton Pyle, a member of the rich and politically powerful Pyle family and the head of an administration “rife with scandal, military misadventures, diplomatic gaffes, and fiscal irresponsibility.”

Sound familiar? Well so does Colgate, whose greatest impediment to the presidency is his chronic philandering and womanizing. There’s more than a little evidence here that Truman used bits of politicians past and present in writing the book.

None of the presidential campaign characters are particularly engaging. Instead, the best part of “Murder Inside the Beltway” is the cops investigating the murder, who slowly uncover a trail of corrupt power that includes every part of Washington. There’s Walt “Hatch” Hatcher, a gruff and weathered homicide detective whose increasing friction with Detective Matt Jackson may have to do with Jackson’s relationship with fellow Detective Mary Hall, possibly because Jackson is a highly educated biracial Chicagoan. (Anyone wonder where Truman thought up someone like that?)

As a rule, nobody in the book is particularly three-dimensional. The biggest problem with “Murder Inside the Beltway” is the major characters aren’t at all believable, and while the minor ones are more so, they still are lacking. But that is less important: Truman is writing to entertain, not to stimulate — and for the first third of the book Truman is fairly successful. She keeps the reader interested and wondering where the story is going and how it all connects.

Alas, Truman fails to carry that charisma. The big plot twist meant to keep pages turning falls short because it lacks the gravity of something big that could happen in campaign season Washington. The twist involves the abduction of a campaign aide’s daughter. Abductions in real life are no laughing matter, but in the imaginary drama, it’s hard to care.

Another problem is the various plotlines don’t connect as well as they should. Since this is a mystery-thriller novel, the reader doesn’t expect everything to come together until the end, but even after the last page the various storylines just don’t quite piece together as well as they should.

Truman’s strength, and ironically, her weakness, in “Murder Inside the Beltway” is the desire for authenticity. While the story’s participants are flimsily conceived, Truman’s incorporation of actual places in the District such as Adams Morgan and the Mall is pleasant, as are some of the more technical details such as the different police units.

Truman knows that reality takes a backseat to fantasy in the world of fiction; she just doesn’t seem to have applied the factual aspects to where they count the most, like constructing deep and realistic characters. Then again, pretending doesn’t require incredible thoroughness or entirely believable characters. Perhaps all Truman really wanted to do was keep her characters simple so “Murder Inside the Beltway” was just a fun mystery novel like some other incredibly popular cop stories. At the end of one chapter, a dialogue between Jackson and Hall nudges at the answer:

“Wake you?”

“No. I’m watching Law and Order. They really get it right.”