Solid State Society is a made-for-TV movie that takes place after GITS:SAC 2ndGIG.
It's been two years since Motoko Kusanagi left Section 9. No one has heard or seen from her, not even her mentor/confidante Batou, but as the opening makes clear, Kusanagi is still close by and keeping a very close eye on her old friends in Section 9 and the world of cyber crime.
The story begins when a lieutenant of the former dictator of the Siak republic, who himself is taking asylum in Japan, takes a hostage, then winds up killing himself in a fit of panic. But not before revealing "the Puppeteer is coming!"
Section 9 finds that 12 other members of the former Siak president's military guard have also killed themselves. After the former leader of Siak is found dead Section 9 is off and running.
The investigation leads to a child smuggling ring (how the Siak dictator came to be involved in it is never explained) whose beneficiaries are a collective of elderly people, the "Noble Rot Senior citizens," who take the kids as their own. Noble Rot is a group of wealthy, elderly invalids who see in the children a chance to shape Japan's future, and form the children into a national ruling class. Togusa finds out that that the elderly connivers of Noble Rot are in fact the Solid State Society. The Puppeteer it turns out is working hand in hand with them. Why is the reason behind the story.
This is a different world than the one of the first two seasons of GITS:SAC. For starters it's far darker than GIG1 or even GIG2. Section 9 is bigger than ever --over 20 people now, mostly never before seen characters who we never get an introduction to, not even a speaking part. As Aramaki puts it, he wants a group that can cover multiple investigations at a time without using all it's resources. Togusa is now team leader, and a big improvement over Kusanagi IMHO. His cop manner is much more likeable than Kusanagi's lone-wolf routine.
The other thing one notices is that we start to see an introspective Kusanagi. She is more like the angst-ridden moaner from the '96 movie and less like the still-friendly cop from the two SAC series. If one watches SAC:GIG1, then SAC:GIG2, Solid State Society and Ghost in the shell, in that order it's clear how the producers masterfully transform Kusanagi from a person capable of experiencing happiness to a woman consumed by her doubts about her own humanity. If anyone who thinks SAC exists in an "alternate universe" watches the series and the 3 movies, all in order, they'll have no doubts they're all in the same universe when it's over.
I don't have to say anything about the animation for GITS:SAC:SSS. It's feature worthy, and I expect no less from the GITS:SAC Committe. They ALWAYS deliver the goods visually. The writers tell a complex (at times unnecessarily so)
but engaging story, and after a couple viewings you will actually get it all! :D
Solid State Society is a strong entry in the GITS cannon, although it blatantly borrows themes from the '96 movie --former dictator seeking asylum; the "Puppeteer," which sounds almost exactly like the "Puppet Master".
Still it's stronger than GITS:Innocence, but not as "philosophical" as either of Mamoru's works. Those who felt the first movie was too talky and a tad too dark will like this one much better. Although the international politics angle is no simpler the story focuses more on crime-solving and isn't so bleak.
For non-fans this film stands on it's own as a good movie, and will get them used to the gritty, sophisticated world of GITS:SAC, though for the uninitiated it's not the most accommodating place to be introduced to the series. For fans of the series this movie is a must-have, not just because it's another great story in a fascinating universe fans already love, but because it completes Kusanagi's character arc.