She is a significant character to the novel series. Rita is the woman who Dexter uses as a disguise to fit in to society. Dexter's "love" for Rita seems less sincere in the novels than it does in the television series. She has two children from a previous relationship, Astor and Cody, who were abused by their father.
Rita and Dexter are, by a humorous misunderstanding, engaged in Dearly Devoted Dexter and married at the end of Dexter in the Dark. It is never said in the books how they met. In the books, Rita is also something of an exercise fanatic. She and Dexter regularly go for 5k runs, long bike rides, or weightlifting sessions together. In the fifth book, Dexter is Delicious, Rita gives birth to a girl, Lily Anne. In the seventh book, Dexter's Final Cut, Rita is murdered by pedophile Robert Chase after she caught him molesting Astor.
Ex-husband - Rita was married and divorced some time prior to the novel series beginning. Unlike the TV show, Rita's ex-husband is never mentioned by name, and has yet to make an appearance in any sort of capacity.
Deborah Morgan - Deborah is her sister-in-law, from the third book on.
Brian Moser - Brian is her brother-in-law, and realtor.
Brandon Weiss - Rita kicked him twice with her legs (because her arms were still bound) in self-defense which caused him to fall on a table saw. It cut off his arm and he bled to death. (Dexter by Design)