Books can be attributed to "Unknown" when the author or editor (as applicable) is not known and cannot be discovered. If at all possible, list at least one actual author or editor for a book instead of using "Unknown".
Books whose authorship is purposefully withheld should be attributed instead to Anonymous.
First, let's clear up the "unknown author" business. It's a collaborative effort by Ignasi de Sola-Morales, Cristian Cirici and Fernando Ramos. It's part architectural history, and part preservation.
Before Mies became famous (or infamous) for the Farnsworth House, the world was over the moon about the pavilion he designed for the Barcelona Exhibition. This book explains why. I had always been curious as to whether there had been something akin to architectural bread crumbs...something which might explain how Farnsworth House came about...the pavilion might be one of those crumbs... lots and lots of stone...Travertine, naturally, but also two types of green marble...some of it coming from Greece, and some of it coming from Italy's Aosta Valley, tucked in between France and Switzerland. But the real eyepopper was onyx dore, a gold marble quarried in either Algeria or Morocco (and don't get me started on the various shades of tinted glass he used). He spared no expense on this project...which means he spent a lot of other people's money...to do this up right. But what makes this book a fascinating read was that once the exhibition was over in 1929, the authorities...either the Germans or the Spanish, dismantled everything, and it was forgotten until about 60 years later when someone realized just how stunning it was. It's back together now...and the book is a great then and now look and the world of architectural lost and found.