General Sam Lane visits his daughter, Lois, and grandson, Jonathan, for the first time. While this tense reunion is happening, Superman is breaking apart an asteroid that could have threatened the Earth. Within the asteroid, he finds a crystalline material that will help him with a different problem: Cyborg Superman in the Phantom Zone.
Action Comics #999 is an endearing one-off story which remembers what people like about Superman. It also works a good midpoint between "Booster Shot" and the much-hyped Action Comics #1000.
The part of the comic that most sticks out the most is the plot with Superman and Cyborg Superman. This discussion will involve some minor spoilers, so you've been warned.
After his clashes with General Zod's family, Superman has come to realize how psychologically damaging the Phantom Zone can be, and he locked Cyborg Superman in the Phantom Zone not too long ago. Clark builds a new cell for Cyborg Superman in the Fortress of Solitude made from the crystalline material in the asteroid and gives Cyborg Superman a crystal which allows him to relive his fond memories from when he was Hank Henshaw.
That's one of those classic Superman moments that shows his kindness, even towards those who have done things as abominable as Hank Henshaw. Clark knows there is still a man in there, so he does him a kindness. He wants Henshaw to rehabilitate, not suffer.
The Lois Lane and General Lane plotline isn't as compelling. They argue about Superman, but they don't acknowledge each other's points. They just argue past one another. Sam Lane argues that Superman is too powerful to be left unchecked, and Lois says he's a great guy. Yes, Superman would be frightening in theory, but the kindnesses done by Big Blue should warrant him some trust. However, the ending is heartwarming enough to justify its presence in this comic.
Will Conrad contributes the artwork to Action Comics #999, and it largely looks quite good. It has that 3D-rendered aesthetic, and I'm generally fond of it. Sam Lane looks a bit odd at times, but the brief bout between Clark and Cyborg Superman looks great. Ivan Nunes presents some dazzling color work that gives some extra life to the book.
There's also a prominent visual gag about the upcoming #1000, as you can see above.
Action Comics #999 is an all-around feel-good comic. Bridges are mended. Kindness is shown. People bond. Plus, the art is solid to boot. This one earns a recommendation. Give it a read.