Dan Brown, author of "The Da Vinci Code," takes on some whopping metaphysics in his new book, such as: "What happens to the human condition if the great mysteries of life are finally revealed?"

Good question. Pity he doesn't bother to answer it.

Perhaps there are no definitive answers, but when a book alludes to someone's ability to solve, say, the mystery of what happens after we die, a reader expects to learn what that process entails, not to wade through a lot of historical mumbo jumbo about symbols and allegory and how the Freemasons are good guys.

"The Lost Symbol" is full of such empty teases. Maybe the idea is to provoke us to allow our imaginations to roam unhindered by logic. Fair enough. But the book is supposed to be a thriller, and it reads more like a primer. Call it Freemasonry 101.

There are a few chases and several ugly acts of violence, but most of the characters prefer to talk rather than act, which would be fine if only their conversations weren't so repetitive and simplistic and if much of the talking wasn't just a device for the author to set up his deepest perplexities.

This time "The Da Vinci Code's" symbologist Robert Langdon is called to fill in at the last minute as a speaker at an event hosted by his friend Peter Solomon, head of the Smithsonian Institution. At least that's why Langdon thinks he's leaving the relative safety of Harvard in such a rush.

Turns out he has been lured to Washington, D.C., by a madman who calls himself Mal'akh. This sadistic, tattooed eunuch — of course he is a eunuch! — is holding Peter hostage and will only free him if Langdon helps him solve a potentially dangerous Masonic riddle.

Mal'akh, we learn, is a former drug runner who logged time in a Turkish prison and is fond of speaking like a 1940s villain. He also enjoys blood sacrifice. As the race for answers grows more deadly, sending Langdon all over the nation's capital, others become involved. Brown reuses many of the devices that made "The Da Vinci Code" so popular: Famous landmarks play a large role, and he delves into the workings of a secret society.

Stylistically, nothing much has changed. Brown writes short chapters that end on cliffhangers. He could never be accused of being an elegant stylist, and his fondness for cliche is legendary.

Such lapses can be forgiven if you've got a compelling story. "The Da Vinci Code," for all the backlash it inspired, dared to tamper with the tenets of Christianity and to offer up an intriguing conspiracy; its payoff was strong.

"The Lost Symbol" feels more like a lecture that's occasionally interesting but still a lecture, and its payoff is virtually nonexistent.

"The Lost Symbol" by Dan Brown; Doubleday (509 pages, $29.95)