The largest library in the world

The largest library in the USA is also the largest one in the world, i.e. The United States Library of Congress in Washington D.C. It holds the astronomical number of books which are about 118 million items. They require 500 miles of shelving. As seen in these pictures the building is a work of art on its own, with lovely decorations, paintings and architecture. This is a new 'Library of Alexandria', a one which should be preserved, even in the modern digital and internet epoch we live in. 

But I am not sure if it has the largest book in the world. This book contains 10.000 pages. It belongs to the University of Iowa and is called 'Marathon of Poetry' and is considered the 'fattest' book to ever be printed. This book was created for the celebration of "The City of Literature" from UNESCO.