If someone feels the need to tell me that their book is based on a true story, there is probably something seriously wrong with the work. Such as:
1. It is a quickly worked-up novel based on a sensational news story, whose author is hoping to cash in on the morbid rubberneckers in the audience. It tells me that the author was too lazy to create their own characters, plots, and situations.
2. It is a badly researched bit of history, biography, or crime drama that is called a "novel" simply for convenience (and maybe to attempt to avoid a lawsuit). It tells me that the author was too lazy to complete the research and get the facts right.
You can bet your boots that anything touted to be "based on a true story" is going to be an artless piece of trash.
But here's where things start getting tricky. Does that mean that all books based on true stories are trash? Of course not. Only the ones that are advertised as such by the authors or their publishers--the ones without literary value that appeal solely to the morbidly curious. One of the most famous pieces of "journalistic fiction" is Truman Capote's 1966 book, In Cold Blood. Dubbed by some critics as heralding a new form of crime reporting, it was labeled fiction by others because of changes Capote made in several scenes and for his re-creation of dialogue. Not to be outdone by his literary nemesis, Norman Mailer released his own piece of literary crime writing, The Executioner's Song, which chronicled the life and bad deeds of murderer Gary Gilmore. The book won the Pulitzer Prize in 1980 for--you guessed it--fiction. Capote's book entailed six years of research and thousands of pages of notes. Neither he nor Mailer had to rely on "Based on a true story," to win sales and accolades.
The famous novelist E. L. Doctorow wrote a fictional account of the lives of Julius and Ethel Rosenberg in his highly praised 1971 novel The Book of Daniel. His next novel, Ragtime, used a combination of fictional and made-up characters in his intriguing story line. Was it based on a true story? Who cares; it was a great book and I enjoyed reading it.
That brings us to copyright page disclaimers. You know what I mean: "This is a work of fiction and any resemblance between the characters and persons living or dead is purely coincidental." This is the actual text on the copyright page of Charles Bukowski's novel, Hollywood, which is a scathing roman à clef of the making of the movie Barfly. Is it fiction? Some of it probably. Is it based on a true story? Of course--everybody on earth knows this and no disclaimer can make it otherwise. There have been discussions of exactly how to word such a copyright disclaimer. What if only some of the things are true, what if the college is real but the basketball coach fictional? What if the stories are true but "the names have been changed to protect the innocent."?
Well here's a news flash. Every novel has at least a bit of truth, and most of them have more than a little. I've never written a novel or a story that doesn't have a great deal of myself in it, that doesn't use the mannerisms of someone I've met or observed, that doesn't use certain accents or colloquialisms I have heard from others, that doesn't describe living rooms or gardens of my friends and acquaintances. Again, any thinking person knows this. To have to add a disclaimer saying it isn't so, Joe, is just silly. It's a lie and everybody knows it's a lie.
Now I admit that it is wrong--and illegal--to write about a real person, either by name or giving that person a pseudonym, and insinuate that this person has committed a crime or done some other unsavory act without direct proof. And writing about real people can have consequences. When Thomas Wolfe wrote Look Homeward Angel, using thinly disguised versions of his family, friends, and home town, he was unable to return home for eight years due to the negative furor from those he wrote about. Worth Tuttle Hedden's marvelous novel Love Is a Wound is a similar effort. The biographical detail of the novel is part of its greatness and helps make it the culmination of her life's work.
So my advice to people who worry about exactly how to word their copyright disclaimer or their "based on a true story" blurb is this. Just hit delete.