Who is Castle?
Richard Castle is the main character of the show. He has one daughter and his mother lives with HIM. Not the other way around. He is the author of two books, Heat Wave and Naked Heat and they are actual books. If you read his homepage you would know that he works with Detective Becket on her crime cases. He also has an incredibly funny sense of humor and sarcasm. While working in cases he always conjures up impossible solutions which are casually dismissed by Becket. He's a great character.
Picture of Castle
picture found on http://www.tvovermind.com/wp-content/uploads/2009/07/richardcastle.jpg
Who is he played by?
His character is played by Nathan Filion.