Landen Park-Laine is Thursday's on again, off again husband through out the series. Landen is a successful writer in the beginning of the series, though his popularity seems to wane in the later books. He is featured in every book in the series.
In The Eyre Affair, Landen is Thursday's ex-boyfriend. After the Crimea, Thursday left him because of what happened to her brother. After Thursday returns to Swindon, Landen repeatedly tries to get back together with Thursday, despite Thursday's attempts to keep away from him. Once he becomes engaged, however, Thursday tries to win him back. In the end, Landen's original wedding plans are canceled and he marries Thursday.
In Lost in a Good Book, Landen is enjoying the beginning of a happily married life with Thursday. The two learn that Thursday is pregnant with their first child (as is Pickwick) and Landen tries to teach Pickwick to stand on one foot for a marshmallow. Not long into their marriage, however, Goliath has him erradicated at the time he was about to drown when he was two years old. After his erradication, Thursday often dreams about him. Thursday and her father attempt to reactualize him, but fail.
In The Well of Lost Plots, Landen is once again featured only in Thursday's memories. Slowly, Aornis Hades attempts to make Thursday forget about her husband, while Granny Next tries to help her remember him. Thursday's memories of Landen are eventually saved.
In Something Rotten, Landen is finally being reactualized by Goliath in an attempt to win Thursday's forgiveness. He flickers in and out of existence, making the situation hectic as Thursday tries to be with him when he is there and save face when he's not. Landen doesn't entirely believe Thursday's story about the past couple years at first, but eventually does once he meets several of the book people Thursday described. Once Thursday recovers from being shot, he is very relieved and they finally start their life together.
This book also features Landen in his very own chapter. In this chapter, Landen is now the narrator and describes his feelings as he awaits the good or bad news about Thursday's condition.
In First Among Sequels, Landen is the happy father of two (three, according to Thursday) whose popularity as a writer has plummeted. Despite Thursday's efforts, to keep the truth about her continued SpecOps work and Jurisfiction work hidden, Landen has known about it for almost as long as she's been at it. Landen, along with Friday and Tuesday, try to help Thursday through her episodes in remembering that there is no Jenny. Landen is supportive of Thursday throughout the book.