"40" is a very modern multi-perspective television drama, with plenty of hand-held camera work and rapid cross-cutting between scenes, telling its story in the minimalist fashion favoured by writers such as Tony Marchant (the stylistic resemblances to "Holding On", in particular, are clear). It features one neat trick that takes advantage of its economical style, in that it's actually slightly less compact than it seems: having been shown one selection of scenes, we subsequently return to the same events and see a slightly, but revealingly, different selection. At one level this is entirely bogus: as the different versions of the story do not correspond with the viewpoints of any particular character, the choice of what to show where is arbitrary and contrived. But it feels "natural" while you are watching it; at least, the handling of the plot is in keeping with the overall form of the work. In that sense, "40" can be considered a qualified success.
But ultimately the tale, though neatly done, falls slightly flat. Crucially, a lot of things happen but to little greater purpose: the particular details of each incident, even the showpiece school reunion, tend to feel little more than purely incidental. The lives of the characters are too disconnected to make a really satisfying whole: there's no real focus here, simply events. The actual story of each individual, meanwhile, doesn't really add up to much; and whole it is nice to see Joanne Whalley back on British television, her character, Jess, remains a mystery to us. Ultimately, a more traditional drama, with a closer affinity to fewer characters, and a less trendily efficient style, might have allowed a deeper story to emerge.
"40" isn't bad, but it seems to fit a paradigm for how to make television in 2003, namely, sketch several stories in outline only, then mix up their pieces and hide the thin treatment of each behind the breadth of the whole. This can work, as "Holding On" showed; but that serial had more depth and a unifying mood. "40" has neither. In a few years time, it will surely show it's age.