ThecoreofthebookisaboutthecoreApacheHadoopproject,andsincethe3rdedition,Hadoop2hasstabilizedandbecometheHadoopruntimethatmostpeopleareusing.The3rdeditionactuallycoveredbothHadoop1(basedontheJobTracker)andHadoop2(basedonYARN),whichmadethingsabitaw