THE ARCHITECTURE OF FRANK GEHRY; foreword by Henry N. Cobb (Rizzoli: $45, hardcover; $29.95, paperback). At last we have a book that begins to explain the provocative and increasingly pronounced designs of Frank Gehry, one of Southern California's more prolific and controversial architects. Well illustrated and designed, the book consists of a series of essays tracing Gehry's career, accompanied by a commentary by the architect himself. While the respectful, topical essays by, among others, UCLA professor Thomas Hines and architecture writers Joseph Giovannini and Pilar Vilades are informative, it is Gehry's candid comments concerning each of his projects that are the most revealing and engaging. The book was published in conjunction with a retrospective exhibition of Gehry's designs at the Walker Art Center in Minneapolis, an exhibition that is scheduled eventually to make its way to the new Museum of Contemporary Art here.