The Maltese Falcon and The Big Sleep are often considered the two greatest acheivements of detective noir prior to the post-war era.  It's by no means incidental to their reputation that both starred the pitch-perfect Humphrey Bogart, nor that in both films, he portrayed a classic private eye created by one of the standout pulp witers of the previous decade.  Though both have been rescued from dime-novel oblivion by later critics who were able to pick out their substantial literary talents from the low-level hackwork that comprised much of 1930s pulp, Raymond Chandler's reputation has outstripped Dashiell Hammett's, and rightfully so; Hammett was an outstanding technician and a keen drawer of character, but he lacked Chandler's transcendent style, his keen psychological insight, and his stunning sense of place and time.  Still, he shared with Philip Marlowe's creator a love of language, and he was by far Chandler's superior in terms of complex, inventive plot, which made his books natural fodder for movie adaptations.

In his finest book, The Maltese Falcon, he combined this exquisite sensibility for clockwork plots with some of his most sinister and intriguing characters (the pathological lying femme fatale Brigid O'Shaughnessy, the effete and manipulative thief Joel Cairo and the gregarious but sinister crime boss Kaspar Gutman), who he sent off in search of cinema's most memorable MacGuffin.  Against them all he set the coolest, most calculating private eye in all of literature:  the immortal Sam Spade.  Much like its spiritual twin, The Big Sleep, The Maltese Falcon, despite a number of divergences from its source, achieves near-perfection and serves as an unforgettable 1941 movie adaptation that makes you appreciate the finer qualities of the novel all the more.

WHAT IT HAD: John Huston, one of the greatest directors of his era and the man who is far more responsible than either Humphrey Bogart or Dashiell Hammett for the film's success.  Huston adapted the screenplay himself, stripping the story to its most raw elements, losing as little as possible while streamlining for the screen and keeping Hammett's understated, cooly cruel dialogue intact.  An amazing cast with not a flat performance in the bunch -- aside from Bogart's iconic performance, Mary Astor gives the role of a lifetime as Brigid, Elisha Cook Jr. plays nicely against type as the furious gunsel Wilmer, Peter Lorre's Joel Cairo is endlessly entertaining, and Sydney Greenstreet's Kaspar Gutman is simply one of the best screen villains of all time.

WHAT IT LACKED: Very little.  Thanks to Huston's top-notch direction and wonderful sense of timing, the parts of the novel which are left out are hard to miss, and the dialogue is so well-translated to the screen that you don't too much lament the loss of Hammett's fine style (as when he describes Spade, early on, as "rather pleasantly like a blond Satan").  Bits of exposition are left behind to no great loss, as well.  Perhaps the major difference between book and movie can be chalked up to the Hays Code:  censors of the day wouldn't allow Joel Cairo to be portrayed on film as he is in the book as obviously homosexual, and the book is far more violent than the film -- scenes where Gutman tortures his own daughter and is himself ultimately murdered by the betrayed henchman Wilmer Cook are deleted. 

DID IT SUCCEED?:  Both the book and the film are nearly perfect examples of their kind.  Ironically, at the time the movie -- a huge critical success, then and now -- was made, the author of the the novel, Dashiell Hammett, was not taken very seriously.  At the time, almost all pulp writers were considered low-rent hacks cranking out peurile entertainment for the masses.  The movie, however -- which featured a screenplay by John Huston that mirrored the plot and dialogue of the novel almost exactly -- was hugely praised by critics both highbrow and popular.  In fact, Huston received an Oscar nomination for the screenplay, while Hammett would wait some 30 years (a decade after his death) to receive a serious reappraisal by literary critics.