Kevin Smith's reputation has always been contingent on your relationship to the specific cultural and personal universe his films inhabit. Clerks arrived in 1994 as a document of a generation's particular brand of paralysis: intelligent, over-educated, stuck in jobs they were too smart to respect and not ambitious enough to leave, talking endlessly about the pop culture that had partly produced them. It worked because Smith was writing from inside that experience rather than from above it, and the film's scruffiness was itself an argument about the condition it was describing. The films that followed varied wildly in how successfully they maintained that inside position, and the ones that failed tended to fail because the self-awareness that made Clerks honest became something more defensive and self-regarding. Clerks III finds Smith working from the inside again, and the result is the most genuinely moving entry in the View Askewniverse since Chasing Amy.
Randal (Jeff Anderson) suffers a heart attack at the Quick Stop and, in its aftermath, resolves to make a movie about his life with the help of Dante (Brian O'Halloran) and the usual suspects: Jay and Silent Bob (Jason Mewes and Kevin Smith), Elias (Trevor Fehrman), and, in a way that the film earns the right to handle, the memory of Becky (Rosario Dawson, reprising from Clerks II). The film-within-the-film conceit, in which Randal recreates scenes from his own life while making a movie about it, allows Smith to revisit Clerks with the same cast and the same locations thirty years later and to do so in a way that is not primarily nostalgic but primarily elegiac.
The structure is clearly delineated into three parts. The first, covering the heart attack and its immediate aftermath, runs a little long and is the section most likely to test the patience of viewers who are not already invested in these characters, particularly in the Elias material, which has always been the weakest thread in the Clerks sequels. The second, in which Randal and Dante make their movie, is where the film hits its stride: the recreation of original Clerks scenes with original cast members returning to their roles is both funny and quietly devastating in ways that only work because Smith has earned the specific sentiment through the accumulated history of these characters. O'Halloran gets the most dramatic material of his career in the film and handles it with a precision that the role probably appeared to not require back in 1994.
The third act is the film's reason for existing, and it is not fair to describe it in detail. What can be said is that it resolves the Clerks trilogy with a completeness that the original could not have anticipated and that Clerks II was working toward but did not fully reach. The View Askewniverse has always been built around the specific friendship of Dante and Randal, and the film's closing sequence is the most honest thing Smith has committed to the screen in the service of that friendship.
For anyone who has followed these characters across thirty years, it is essential. For anyone new to the franchise, start with Clerks and work forward.
