Orlean is an outstanding writer - she manages this by inserting herself into the story, in the tradition of the best non-fiction writers (such as Mary Roach or Rebecca Skloot). First, she tells you why she didn't want to write the book (or any book), and then she tells you why she had to write this one. Along the way, she tells you the story of libraries, writ large.
It's no surprise that there are a billion reasons for the need and service that libraries perform, from the kind and quantity of questions that are asked of LA Public librarians on a daily basis to the preservation efforts of all libraries, even when there isn't a natural disaster to contend with. (Yes, I'm a librarian, but that's still all true.)
The LA Public Library fire was and remains one of the worst in history. A heartbreaking number of unique and irreplaceable items were lost, and as with many fires, there's no doubt that the age of the building and its construction played a part in the difficulty of extinguishing the fire. Orlean tells the tale from the vantage point of being new to town and giving her son an introduction to the town's services. She also tells the tale with a sense of disbelief at how invisible the story of the fire has become over the years.
She interlaces fact and storytelling as only she can do. There's nothing dry about this book, and nothing poorly described. You will learn a ton about the value of libraries and their services, but you will learn more about one of the more absorbing "hidden in plain sight" tales out there.