No ship in history has the notoriety of the Titanic. There are more than 130 books inspired by the doomed liner. Google supplies 3.5 million references. More than a dozen motion pictures are devoted to the disaster, and the last one, James Cameron's 1997 award-winning "Titanic," no doubt has shaped many people's opinions about what happened the night of April 14, 1912. All of which begs the question: Do we really need another book on the subject? In the case of Brad Matsen's "Titanic's Last Secrets," the answer is yes.

Matsen's narrative revolves around the dives to the Titanic by John Chatterton and Richie Kohler, two professional wreck divers who discovered the German submarine U-869 off the coast of New Jersey and were chronicled in "Shadow Divers."

Chatterton was approached by David Concannon, a Philadelphia lawyer and explorer, who had spotted "ribbons of steel" in a dive to the Titanic in 2000. The "ribbons of steel" were plates from the Titanic's hull, and the men hoped that further photography/analysis of the steel might reveal more about the ship's final hours.

To find out, Concannon, Chatterton and Kohler assembled a team consisting of, among others, photographers, a naval architect, a marine forensic expert, a historian familiar with Titanic class vessels, and a U.S. Department of State representative schooled in wreck and salvage treaties. They chartered the Russian ship Keldysh and its two Mir submersibles for eight days in August 2005 to find the hull.

On the last dive of the last day in 2005, Chatterton and Kohler found two large pieces of the Titanic's double bottom, its keel and bilge keels that ran along both sides of the ship. Their discovery changed theories of the Titanic tragedy. The two bottom pieces, found many yards apart, showed no signs of grounding. The pieces were torn from starboard to port, not along the keel. Incredibly, when photographs and drawings of their jagged edges were put together, they matched perfectly. The team had seen and documented exactly where the bottom of the Titanic split apart.

But photographs of the broken edges puzzled the experts. The steel showed more signs of tension than compression, and the upper deck steel revealed evidence of compression. To naval forensic experts, this suggested that the Titanic at first had bent in half downward, like a shallow V, snapping the double bottom in two, then bent upward, like an inverted V, ripping the top decks and hull in half. Contrary to all accepted theories, they concluded that the Titanic's stern did not rise out of the water at a steep angle and then break apart.

The Titanic flexed near midship after hitting the iceberg, they concluded, because the structural integrity of the ship was not what it should have been. The separation did not happen underwater. It did not happen because the ship rose steeply out of the water and the weight of the stern pulled it apart. The ship broke in half on the sea's surface, then it sank.

The materials were neither of the quality nor mass required by a ship the Titanic's size. The original specifications of its designer, Thomas Andrews, were not followed in order to reduce the cost of building the ship, they suggest. The Titanic's designer had specified 1.25-inch-thick hull plates, but Bruce Ismay, president of White Star lines, insisted on 1-inch plates to cut the ship's weight and coal consumption. The rivets were also reduced by Ismay.

To confirm the "weakness" theory, Chatterton-Kohler met Tom McCluskie, who worked for Harland & Wolff, the company that built the Titanic. He had access to the company's archives and confirmed the theories of the Chatterton-Kohler team.

In addition, the team dove to examine the sunken Britannic, a sister-ship of the Titanic, launched in 1914, and supposedly built to the same specifications as its famous predecessor. As they suspected, the Britannic dive revealed several design changes made by Harland & Wolff.

Had the Titanic been built to the engineers' original specifications, it might not have sunk so quickly, allowing more time, perhaps, to save hundreds of lives.

That is the central thesis of this new book, which also includes many photographs, drawings and excellent profiles of key figures in the Titanic's history. "Titanic's Last Secrets" does not answer all the questions this famous disaster poses, but it offers tantalizing new details that pique one's interest. That is one sign of a good book.

W.E. Mueller writes from Chesterfield.