National Treasure: Book of Secrets makes no attempt to disguise its sources. Like its predecessor, this outing functions as kind of a low-rent variation on the Indiana Jones films, and bears the distinct high-gloss production stamp of Jerry Bruckheimer. This is the cinematic equivalent of cotton candy, and gives us virtually nothing substantial to take away from it. And yet, on a completely sophomoric, mechanical level (and even at an excessive 123 minutes) the film feels aggressively enjoyable. It's an undemanding, carnivalesque thrill-ride that whisks the audience off on a high-flown string of adventures, with a host of urban legends that seem pulled straight from brazen adolescent fantasies. We're given desks with secret compartments that house strange carvings, an ancient city of gold buried in booby-trapped caverns beneath a national monument, and a presidential "Book of Secrets" containing every long-buried skeleton that the U.S. government doesn't want us to know about. All of this is gleefully absurd, of course, but for those willing to accept the film's high-flung fantasy and nonetheless suspend reality in their minds, NT2 provides more than its share of kicks and thrills. By the 90-minute mark, when the protagonists reach the said cavern, one feels that one has fallen into a big-budget movie version of the old arcade game Pitfall 2; Book provides the same sorts of hijinks and setpieces. It also feels refreshing to see actors as brilliant and as serious as Harvey Keitel, Jon Voight, and Helen Mirren (in supporting roles) let their hair down and have a good time with material that is knowingly ridiculous. Unfortunately, if Bruckheimer -- sensing the closure of the Harrison Ford-starring Indiana Jones vehicles with Crystal Skull, given Ford's age -- wanted to unofficially spin-off his own franchise, he made a poor choice with the creation of Treasure's lead character, Benjamin Franklin Gates (Nicolas Cage). Part of what makes the Jones films so much fun is their ability to spin outrageous whoppers yet, thanks to Ford, retain a deeply human, incredulous, self-deprecating protagonist with a sarcastic sense of humor and at least one major Achilles' Heel. (Read: snakes). Cage never gives us that balance, not even once. His Gates is a kind of patriotic Übermensch, a walking historical encyclopedia implausibly rife with facts and figures and seldom, if ever, prone to making slip-ups (nary a one in sight, here). And perhaps as a result, it becomes almost impossible to empathize with him. Director Jon Turteltaub, Bruckheimer, and scriptwriters Cormac and Marianne Wibberley attempt to compensate for this by giving Gates as an assistant a sophomoric, goofball hack named Riley Poole (Justin Bartha); it doesn't work. One can also fault Bruckheimer for some self-indulgent excess -- apparently it is no longer necessary for him to even put his surname under his production company identification at the beginning of the picture, because here the logo appears without a name; instead, he trademarks his involvement in the film with a couple of gratuitous and unnecessary car chase scenes that the film could very easily do without, and that seem purely designed to let Jerry unleash his destructive, adrenaline-fueled urges and identify his presence. Spare us. But these moments are primarily limited to the film's initial half-hour, and after that, the picture sinks into an exciting, groovy rush and even begins to recall the old-time Saturday matinee serials as Raiders of the Lost Ark did. Taken for what it is, and approached sans expectation, Book of Secrets should please many undemanding viewers, especially teenage and preteen males, with its roller coaster-like ride of thrills. It's surprisingly fun.