Twin Spica is at its heart a serious anime set in the near future about a girl who wants to become an astronaut. NHK seems to be into the space-themed anime this year, but Twin Spica is a lot different than Planetes in its drama and characterization. Planetes seems to be pretty sci-fi, but Twin Spica is more like a character-driven drama that happens to involve space. ^^
As opposed to the manga, the anime for Twin Spica starts off when Asumi is just entering elementary school, right after her mother dies. Her mother had been in a vegetative state for five years after the explosion of a rocket at launch that devastated the town in which they lived. Asumi never knew her mother aside from pictures and a bandaged figure on a hospital bed, but when her mother dies, Asumi takes the box with her remains to try and give her a better place than she had when she was in the hospital room. On her way, she meets a ghost with a lion head playing the harmonica. She befriends him and eventually gets him to help her take her mother's remains to get a good view of the sea that she loved so much when she was alive. The ghost, Asumi's teacher, her mother, and the space program are all interconnected, and I don't really want to spoil the drama of episode one for you, so I'll just leave it at that.
The main part of the series actually focuses on Asumi in middle school, where she is trying to decide what to do with her future. She wants to be an astronaut, but attending the space university in Tokyo is expensive! The lion-ghost, her best childhood friend, helps her on her way as she makes important decisions about her future, and as you can imagine, she attends the space university where she makes good friends. The anime so far is a very nice conversion of the manga, so I expect it to follow it pretty truly. The manga actually starts with Asumi in middle school and goes back to this starting point as a flashback, but I think it works well either way.
I orded the Twin Spica manga on a whim after Amazon Japan recommended it to me, but it's probably been my favorite purchase of the year. The story is well-told, the characters are believable enough to make the drama worth watching, and Lion adds a nice touch of fantasy to the series. The great OP by recent newcomers Buzy only adds to my enjoyment of this series, and makes it my absolute favorite show out of the season.