Almosttwodecadeshavepassedsincetheappearanceofthosegraphtheorytextsthatstillsettheagendaformostintroductorycoursestaughttoday.Thecanoncreatedbythosebookshashelpedtoidentifysomemainfieldsofstudyandresearch,andwilldoubtlesscontinuetoinfluencethedevelopmentofthedisciplineforsometimetocome.
Yetmuchhashappenedinthose20years,ingraphtheorynolessthanelsewhere:deepnewtheoremshavebeenfound,seeminglydisparatemethodsandresultshavebecomeinterrelated,entirenewbrancheshavearisen.Tonamejustafewsuchdevelopments,onemaythinkofhowthenewnotionoflistcolouringhasbridgedthegulfbetweeninvuriantssuchasaveragedegreeandchromaticnumber,howprobabilisticmethodsandtheregularitylemmahavepervadedextremaigraphtheoryandRamseytheory,orhowtheentirelynewfieldofgraphminorsandtree-decompositionshasbroughtstandardmethodsofsurfacetopologytobearonlong-standingalgorithmicgraphproblems.