This season there is an anime called Mahouka Koukou no Rettousei (The irregular at magic high school). This anime is based on the light novel of the same name and that can be read on baka-tsuki. There are also a few manga that are related they are short and mostly side stories. The manga can be read on batoto. The anime is one of my favs for this season but I feel that many people may not be able to follow along with the anime as the world that the original author created is quite expansive. The anime has been following the light novel pretty closely with the exception being the back-story for the characters and the world that this all takes place in. As someone who has read the light novels a few times (they are that good) I felt that if I could give a little background to the series it might help others to enjoy it as much as I am.
This story takes place in a world where magic has become real through technology. The technology that allowed the use of magic was not some alien spacecraft or anything like that but the natural progression of human technology. Think in the line of TV and how before TVs were created they were thought to be the fevered dreams of a mad man. As technology gets better who knows what will happen in the future. In the future that this story takes place a third war caused by shortages of fossil fuels and food caused the world to be almost plunged into darkness. With the help of the new magic technology and the magicians that wielded this new technology the war ended. Now each country is in an arms race to develop not just the technology that makes new magic work but also magicians that can be used as weapons.
The Brother and sister combo in the story come from one of the great magic houses of Japan. These houses are called the ten master clans. While there are more than ten of these houses the name has just stuck through time. Each of these houses has a number associated to them that is incorporated into their name. The sister Miyuki is a daughter of one of the important people of their clan and also a powerful mage in her own right. Her brother was not gifted with magic when he was born and so has been looked down on throughout his childhood. His mother even tried to give him the ability to use magic through a taboo process that did give him the ability but when compared to the abilities of normal magicians he is still considered to be a dunce. The process that gave him the ability to use magic also stripped him of basically what it means to be human. The story starts at the start of the their high school career where the sister is placed in the top of the class (Bloom) and the brother is a student that is only their to fill in the role as a replacement should any blooms drop out of the school. (weed).
I hope this little run down will help to clear up many of the questions about the series that people might be having and if there you want to read the light novels (I would recommend that you do because they are very good) I will post a link to them below.
Light novels on Baka-Tsuki