On Jan. 15, 1947, the body of Elizabeth Short, 22, was found in a lot near a busy street in Los Angeles. She was naked, drained of blood and cut in half, and her mouth was slashed on both sides to form a sinister grin.

The unsolved murder of the “Black Dahlia” — a nickname for Short derived from her black clothing and from the flower she wore in her hair — has been the inspiration for books and movies, and a near-obsession for police investigators and journalists.

Former Los Angeles Police detective Steve Hodel believes he’s identified Short’s killer — and the reason police never did. In “Black Dahlia Avenger,” Hodel details his two-year investigation into his suspect — his father, George Hodel, a respected physician.

The author presents evidence that his father was responsible for not only Short’s murder, but the deaths of dozens of women. He believes police knew his father was a serial killer, but covered it up for fear that the public would learn of widespread corruption within the Los Angeles Police Department.

From the discovery of Short’s photo among his late father’s belongings through a dizzying amount of evidence culled from documents, newspapers and interviews, Hodel traces the “thoughtprints” leading back to that day in 1947.

In his introduction, Hodel defines thoughtprints as “traces of our self” that our actions leave behind. “A collective of our motives, a paradigm constructed from our individual thoughts, these illusive prints construct the signature that will connect or link us to a specific time, place, crime or victim,” Hodel writes.

One of the most exciting aspects of “Black Dahlia Avenger” is that Hodel allows readers to discover their own thoughtprints. The book includes so much information that it’s easy for the reader to become a detective, picking out connections even if they aren’t referred to in the text.

Short and George Hodel are at the center of “Black Dahlia Avenger.” But, in telling their story, the author also gives a detailed account of Los Angeles in the 1940s and 1950s. He explains the complicated relationship between police and the press, and the history of corruption within the LAPD. As much as it’s about a mystery, “Black Dahlia Avenger” is also about history.

That the book includes so much information, however, is also a drawback. Hodel occasionally becomes lost in the minor details, straying too far from his father and Short. Although all the background ultimately relates to the Short murder, many of the book’s later chapters are extremely tedious.

Hodel manages to be a mostly impartial narrator as he details the various clues — impressive considering that he’s discovered his father was probably a serial killer. Except for an emotional epilogue, Hodel retains his persona of detective, calmly plotting out the facts.

This is fine because the book really isn’t about the author. But it also raises a few questions. What was his emotional state at various points in the investigation? How did his family — and his father’s widow — react to his findings?

But Hodel has enough to deal with trying to answer questions about Short. His case is complicated because his father and many other key players are dead. Other important information sources have been lost or destroyed