With all of the attention Mies van der Rohe has received over the last few years, it's hard to believe that there could be a pair of "undiscovered" buildings begging for even the slightest considerationand receiving none. Such has been the fate, however, of Mies's Krefeld Villas, a pair of neighboring brickresidences of typically restrained elegance built from 1927 to 1930. Their anonymity is, to some degree, Mies's own doing; in 1959, in his only public comment about the projects, he quipped that he would have preferred to use more glass, but the clients objected. "I had great trouble," he said.<p>As historians Kent Kleinman and Leslie van Duzer show in this carefully researched, eminently readable study, sometimes it's best not to take the architect at his word. Here they guide us through the two villas, which were converted into a joined museum of contemporary art after World War II. Each chapter begins with a study of an artist who has created a site-specific installation within the villas. By analyzing how Yves Klein, Sol LeWitt, Richard Serra, and Ernst Caramelle chose to engage Mies's architecture, they arrive at a truly original understanding of these two forgotten masterworks.