“The unknown is where I want to be,” says Roni Horn, an artist celebrated for her cerebral, wide-ranging body of work in which she explores mutability—of identity and gender, natural landscapes and phenomena, language and meaning. Grounded in Minimalism and shaped by language, Horn’s sculptures, drawings, prints, photographs, books, and installations reveal the subtle, moment-by-moment shifts in an expression, nature, or the meaning of words on a page. In Becoming a Landscape (1999-2001) and Still Water (The River Thames, for Example) (1999), she presents a series of photographs of the Icelandic landscape and of the Thames, respectively, that convey their state of unending change. In addition to Iceland and water, Horn focuses on Emily Dickinson’s poetry and her own androgyny. In a.k.a. (2008), she documents the mutability of her identity—at one the wellspring for all of her work the …