The architect Louis Kahn, who died in 1974, is known for his spare, geometric institutional work like the Salk Institute for Biological Study in the La Jolla section of San Diego and the Yale Center for British Art in New Haven. The 2003 documentary “My Architect,” directed by his son, Nathaniel Kahn, highlighted those buildings, along with Kahn’s romantic life. The architect had three children, with three different women, two of whom were professional collaborators. A new book, “The Houses of Louis Kahn” (Yale University Press, $65), provides an architectural bridge between the personal and the professional stories, focusing on the nine houses Kahn completed, and designs for two dozen more.

The story told by the authors, George H. Marcus and William Whitaker, is one of warm client relations, attention to the smallest domestic detail and a philosophical search for the best arrangement of rooms to call home. Marcus, an adjunct assistant professor in the history of art at the University of Pennsylvania, spoke about it by phone late last month. (This interview has been condensed and edited.)

Q: What was the genesis for the book?

A: It started with a curatorial seminar at the University of Pennsylvania on Louis Kahn’s furniture and interiors. When Bill Whitaker, curator and collection manager of the Architectural Archives at Penn, and I looked through the thousands of drawings in the Louis Kahn archive, we saw a totally different architect there. We focused on his statement that architecture begins with the making of a room.

Q: How does that apply to the house?

A: We believe that the whole search in his design of houses is for the idea of home. Kahn had never had a home. He was an immigrant, he came from Estonia when he was about 5, and he had 11 addresses between the time he entered elementary school and the time he entered high school. When he married, he and wife, Esther, moved into his wife’s family home. It was only supposed to be for a short time, but they lived there for 37 years.

Q: What is the state of his nine houses today?

A: Three of the houses are still owned by the original families, which is quite extraordinary.

One, the Esherick House, has been on the market. That’s one of the houses that people usually call the iconic Kahn house. It was built for a single woman, so it only has one bedroom, but the architectural historian Vincent Scully described it as “a brimming chalice of light.” The Weiss House near Norristown, Pa., is also on the market. The Fisher House has been preserved. The Fishers left it to the National Trust for Historic Preservation, but they realized you can’t make a museum out of every house. There are certain restrictions put on the house so that it will be preserved for the future, but it was sold to a private client.