Reviews for Phase Null are generally more positive than for the previous prequel, The Kill Order , though opinions vary on its necessity:
Thomas and other "immunes," including Teresa, Newt, and Minho, are raised in a sterile, clinical environment where they undergo rigorous psychological and physical testing. Dashner, James [Die Auserwählten 05] • Phase ...
A pivotal moment occurs when a Flare outbreak among ANGST staff forces Thomas and others to participate in a "Purge"—a systematic execution of infected adults to protect the project. Reviews for Phase Null are generally more positive
His journey from a passive subject to an active participant in building the trials provides deep context for his later leadership and guilt. The Kill Order