On one level, the new HBO film "Too Big to Fail" (which debuts tonight at 9) has no business being as suspenseful as it is. Nearly every character is either an investment banker or a financial policy wonk. The subject matter - the mortgage crisis of 2008 - is so complicated that several times the movie has to stop so characters can explain things in layman's terms (usually to people who'd already be able to do the same). And everyone going into the movie will know roughly what happened with that crisis, and that our economy is still a mess.

But it's a credit to the reporting of Andrew Ross Sorkin, whose book provides the template for the movie, and to the screenplay by Peter Gould ("Breaking Bad") and direction by Curtis Hanson ("L.A. Confidential"), that "Too Big to Fail" is able to function as something of a thriller even though the subject matter is dry and the outcome so familiar. It's ultimately not as ambitious or as powerful as, say, HBO's AIDS docudrama "And the Band Played On" (which starred Matthew Modine, who here has a small role as the CEO of Merrill Lynch), but it's more effective than you'd expect, even given the huge amount of talent in front of and behind the camera.

The movie's a veritable who's who of middle-aged character actors (plus a few younger types like Topher Grace), headed by William Hurt as Treasury secretary Hank Paulson, James Woods as Lehman Brothers CEO Dick Fuld, Paul Giamatti as Federal Reserve chairman Ben Bernanke and Billy Crudup as Tim Geithner, among many, many others. It's a cast so loaded that John Heard can appear for about 60 seconds as Fuld's number two at Lehman and disappear without there being any kind of noticeable talent drain on the movie.

The mortgage crisis is such a sprawling, complicated story that the film wisely focuses on the days immediately before and after the Lehman bankruptcy, and the passage of the TARP bill, using those two events as stand-ins for the larger rot in the financial system. Though the subject matter is dry, the conversations are delivered with such conviction by Hurt, Crudup and others, the direction by Hanson is so smooth, and the score by Marcelo Zarvos so effective, that you may be surprised to feel a little adrenaline pumping as, say, Paulson orders a group of investment bank presidents (played by the likes of Bill Pullman, Tony Shalhoub and Evan Handler) to come up with a private solution to bail out Lehman.

Ultimately, there's only so much Hanson, Gould and company can goose the subject matter. And outside of the occasionally awkward long expository scene (with Cynthia Nixon as one of Paulson's aides filling the "explain it to me like I'm a 5-year-old" infodump spot), the movie is at times a little too aware of what happened after TARP passed. There's a scene towards the end, for instance, where Bernanke and Paulson contemplate the many ways their plan could - and ultimately did - go wrong that might as well feature cartoon anvils hanging over each of their heads. Other similar HBO films ("Barbarians at the Gate," "Recount") have tried to tackle this kind of subject matter by taking on a satiric bent; this is more sober, always aware of just how much trouble the U.S. economy - and the world's economy - was in as all these banks fell apart.

Overall, though, "Too Big to Fail" the movie, like "Too Big to Fail" the book, takes a topic that could have felt like homework and turns it into effective entertainment - even if that entertainment might teach you something along the way.

Alan Sepinwall may be reached at sepinwall@hitfix.com