Compared to New Jersey's largest municipal library, Newark, Princeton spends four times as much per capita, and has nearly double the number of visitors and circulation in absolute terms despite a tenth the population.
The house came into the ownership of Princeton University, which rented it to the library for $1 a year.
The new building and the library's new logos and signage were designed by Hillier Architecture.
The building is named for George and Estelle Sands, who made a $5 million donation, with half going to provide an endowment.
The J. Seward Johnson Charitable Trust donated $1 million and the university $400,000.