Detective Traditions:
These indicate tendencies, not absolutes

 
 
Classic Tradition
Hardboiled Tradition
writers like Poe, Doyle, Christie writers like Hammett, Chandler, Ellroy
detectives like Sherlock Holmes detectives like Sam Spade, Philip Marlowe
mystery starts out complexly, finishes simply mystery starts out simply, finishes complexly
seemingly disperate clues fit together into a clear pattern by the end simple beginning leads to more clues, more characters, and an overwhelming pattern by the end
one villain is guilty at the end everyone is guilty of something
wide cast of characters all have motives, but only one did crime wide cast of characters all have a motives, and everyone contributes to the crime
incredibly smart, detached detective restores momentarily disturbed order flawed detective seeks out small justice, but discovers world is too complicated
detective just likes puzzles, solves mysteries for pleasure detective is intimately involved in the mystery; is either paid, or is seeking out something about his or her identity
detective's own identity is never threatened detective is unsure of his or her identity by the end
detective uses reason, science, fact, math, logic, common sense detective uses guts, instincts, emotion, intuition, fallible feelings
detective works with, but is smarter than, authority (cops, adults) detective is rebellious against autority; tries to solve mystery before or instead of autority
authority is righteous at end; takes away villain authority is corrupt; institutions cannot be trusted
the solution of the mystery reveals the order inherent in the world (very conservative) the lack of real solution at the end of the mystery reveals complications in the world (very progressive)
told in a straightforward way, often by an admiring foil (Watson) representing us often told in first person narrative to reveal the flaws of the detective, such as how little he or she knows
mystery is a page-turner, driven by a tension to solve the mystery mystery is more reflective about itself, and how we make meaning of the world
setting is ofen in a single place, such as a parlor, a mansion, a boat, a train setting is often in large spaces, such as cities 
often set in the country, in rich Gothic mansions often set in the corrupt City, in a poor urban landscape
mystery involves movement downwards into basements and caves to represent delving deeper into secrets mystery involves similar types of geographic movement, but represents delving into the self, into tighter confining spaces
mystery longs for and calls forth the Past, where things were better set in the present, concerned with modern problems
villain is clearly evil villain is often someone familiar
villain is something clearly foreign villain is Uncanny, an extension of the Self
comes out of the Modern Tradition, where we beleive science can know the world, and put things in clear patterns comes out of the Post-Modern Tradition, where patterns of knowing are themselves suspect and flawed
mystery is conservative: by defeating villains and solving mysteries, detective makes the world safe and protected again mystery is progressive: in solving the mystery, detective is changed forever - we too are changed as we see a new world

Much of this comes from John G. Cawleti's Adventure, Mystery, Romance.  Consult it for further insights.
 

QUESTIONS TO ASK WHEN READING A MYSTERY