THE SEVENTH SECRET : <i> by Irving Wallace (Dutton: $17.95; 370 pp.) </i>

Irving Wallace can be a crackling good storyteller; in “The Seventh Secret,” he hooks you on the first page and holds you until the last--not an inconsiderable achievement. But it’s not enough, alas--not nearly enough. Not when the writing is as wooden as Wallace’s often is. Not when the plot depends as heavily on coincidence, contrivance and coyness as “The Seventh Secret” does. Not when the subject being mined has already been mined by virtually every pop novelist worth his gestalt.

Nazism? Again Nazism? Did Hitler really kill himself in 1945? Is Eva Braun still alive? Are there underground Nazi loyalists conspiring to raise again the loathsome banner of the Third Reich? The answers are--well, one quickly realizes that “a tall, attractive, older woman named Evelyn Hoffman . . . bears an uncanny resemblance to Eva Braun” (as the book jacket says). As for the rest. . . .

“The Seventh Secret” is the story of Emily Ashcroft, an Oxford historian working with her father on the definitive biography of Hitler. When her father is killed in an “accident,” Emily decides to finish the book herself. In Berlin, she gets to know Tovah Levine, an Israeli journalist who also happens to be an agent for Mossad, the Israeli intelligence agency; it’s a good thing since when Emily (and, perhaps, the entire world) is most endangered, and the Berlin police can’t be trusted, Mossad is on hand. Emily also gets to know (intimately--after all this is Irving Wallace) Roy Foster, an architect who also happens to be a Vietnam veteran; it’s a good thing since when Emily (and, perhaps, the entire world) is most endangered, Foster can call on his knowledge of judo, hand-to-hand combat and even the expert administration of sodium pentathol (“Working from his memory of what he had witnessed in Vietnam, Foster had filled the hypodermic needle . . . “).

At a critical point in the story--perhaps the critical point--Foster must find one of the slave laborers who worked on the construction of Hitler’s underground bunkers. But “there are no slave laborers left anymore,” Foster is told. “Hitler had them exterminated after they finished a job. He didn’t want any of them around to reveal where his various secret bunkers were.”

Dead end? Surely you jest. Nine pages later, a man hired by Emily to excavate the bunker in which Hitler and Eva Braun are supposed to have died tells Foster that his father was a slave laborer who worked on crews that “built most of the underground bunkers during the war.” Dear old Dad was--who would have guessed it?--one of the few such workers to have “escaped and survived,” and his son is planning to see him that very night.

I am no literary snob. The skills of William Gaddis and Jorge Luis Borges are largely wasted on me. But I read a wide range of fiction, and while it would not be fair to hold a writer of popular, mass-market fiction like Wallace to the standards one might expect of, say, Graham Greene, Wallace should be able to churn out a novel as well-done as, say, Frederick Forsyth. Or Robert Ludlum. He doesn’t. Not in this book.

Too often, Wallace conveys what he seems to consider vital information about his characters--or “scholarly” research he has done to prove that he is a “serious” author--with the most blatantly artificial devices. How can Wallace relate Tovah Levine’s background? Easy. “Dreamily sitting on the bench, Tovah was in a mood to reconstruct the last three years that had brought her to . . . “ And reconstruct she does--for the next four pages. Worse, people in this book are forever telling each other in great detail what they would obviously already know. Israeli spies explain to each other things that have already been in the newspapers, for example, and a Berlin newspaper reporter tells Emily things about Hitler that anyone moderately interested in the subject--and certainly someone finishing her research on his biography--would long since have known.

Although most of “The Seventh Secret” is, understandably, concerned with what really happened on April 30, 1945, the day Hitler and Eva Braun are supposed to have killed themselves, Wallace also offers a cheap-shot suggestion by “Evelyn Hoffman” that she and her vile playmates had “come to respect . . . the cowboy president who honored our forty-nine Waffen SS dead in the Bitburg cemetery last spring.”

I am no fan of Ronald Reagan, and I think he was guilty of an especially stupid, insensitive and callous blunder when he visited Bitburg, but to imply, as Wallace seems to, that the Nazis would have found Reagan sympathetic, is repugnant.

I recall enjoying a couple of Wallace’s earlier novels--”The Seven Minutes” and “The Man.” Were my standards lower then? Or are his lower now? Perhaps Wallace should leave politics to other writers and return to compiling trivia, as he did in “The Book of Lists” and “The People’s Almanac” (among others).

Perhaps the eighth secret is that Irving Wallace is not to be trusted with Important Topics. Or is that really a secret?