This nonfiction history of the Library of Congress is highly readable. It's rather slender, as far as adult nonfiction usually goes, and not dry at all. The book is broken up into chapters spanning 50 years each, and talks about the creation of the Library, the succession of Librarians of Congress, and the different iterations and innovations of the Library over the years.
I've visited the Library of Congress three times and work in a public library myself, so I thought I knew quite a bit. I was so wrong! But that's ok; it means that I learned a lot in reading this book. I found myself nearly continually reading little segments out loud to the hubby, I found it all so interesting.
The information is broken up with lots and lots of pictures, all in color (except, of course, the really old pictures where color wasn't available). They are scattered all through the text, not lumped in the middle of the book, and all have clear captions describing the content.