[awkwardpotato]

Modern American printings do now include the final chapter. Described on the back cover as "includes the controversial last chapter not published in the first edition, and Burgess's introduction, "A Clockwork Orange Resucked"".

The "A Clockwork Orange Resucked" introduction is from November 1986. It covers the reasoning behind the shortened American edition[0], Kubrick's film, and his own feelings on the 21st chapter[1]. I think the final paragraph summarizes it well "Readers of the twenty-first chapter must decide for themselves whether it enhances the book they presumably know or is really a discardable limb. I meant the book to end in this way, but my aesthetic judgement may have been faulty" (Burgess xv).

[0] "I needed money back in 1962, even the pittance I was being offered as an advance, and if the condition of the book's acceptance was also it's truncation - well, so be it" (Burgess x-xi)

[1] "There is no hint of this change of intention in the twentieth chapter. The boy is conditioned, then deconditioned, and he foresees with glee a resumption of the operation of free and violent will. [...] The twenty-first chapter gives the novel the quality of genuine fiction, an art founded on the principle that human beings change. There is, in fact, not much point in writing a novel unless you can show the possibility of moral transformation [...] The American version or Kubrickian Orange is a fable; the British or world one is a novel" (xii)