Headquartered in New York City, it was the oldest specialist firm in the United States, focusing on historical and collectible children's books, related original art, and manuscripts.

[2] In 1988, he formed a second corporation—Battledore Ltd, with his partner and spouse Dennis M V David, to further specialize in original children's book illustration art and the legacy of Maurice Sendak.

[10] And as an expert in all things Ozian, Justin appeared in an early episode of the television game show To Tell The Truth (1972) where guest celebrities had to identify him amidst two impostors.

He served on the Lenox Society Steering Committee for Rare Books & Manuscripts at the New York Public Library from 1986 to 2000, and the Lewis Carroll Foundation board of directors from 1988 to 1995.

As an early collector, Schiller formed numerous major collections which resulted in single-owner auctions[15] and exhibitions of what he assembled: Schiller currently lives in Kingston, New York, with his spouse Dennis M V David (together since February 1981, married 27 July 2011),[23] in a Victorian house built for George Coykendall (he managed the Kingston city trolley system for the Coykendall family), above the historic district of Rondout.