It’s an exceptional documentary, even if the second half can’t quite keep up with the first.

If you don’t consider yourself the biggest Steve Martin fan or you need a refresher course on how he became the most popular comedian of the late 1970s, then by all means STREAM IT to the first episode, but everyone should make sure to watch the second part, which provides a much richer, fuller portrait of the comedian, actor, playwright, art collector, and in his later years, husband, father and comedy partner.

This is a thoroughly watchable, intimate and intelligent portrait, although Martin can still be cagey when it comes to family.

The two films could have been combined into one tighter and more effective feature, but even as bifurcated and somewhat baggy as it is, “Steve!” is a smart and charming portrait of a smart and charming man who keeps it all willfully, unfashionably apolitical, and who carefully avoids talking trash about anyone other than himself.

Nothing in the first episode quite prepares audiences for where Neville plans to take them in the follow-up. Sure, the roots of the unhappy dynamic with his dad are there, paying off Martin’s own late-life parenting efforts, but “Now” would likely move people just as well if screened by itself. It’s so different in form from “Then” that the films feel like separate answers to a single assignment, rather than two halves of a complete project. If anything, they’re disconnected pieces of a far larger puzzle.

Martin’s graceful aging and ability to appreciate life more may be less of a yowza story than the meteoric rise that preceded it, but Now still has enough raw material to detail a hell of a second and third act. What we get instead, however, feels remarkably superficial.

Together, the two films in STEVE! handle that task of image reconciliation in a way that sometimes validates Neville’s approach, but in their separateness comes the great frustration of this ambitious project. “Then” isn’t very good and “Now” feels mostly like a very sweet and generally appealing denouement and not a story in and of itself. So “Now” doesn’t work to its fullest without “Then,” and “Then” probably doesn’t work at all without “Now.”