While a book about a large library fire doesn't sound like it would be very relaxing, her descriptions of the library as it was born, and moved, and of other libraries is. The main focus is the fire in 1986 of the Los Angeles Public Library the book is also about the library itself, its history, and its future. 
I love the optimism Susan Orlean leaves us with, about how far the libraries have come in this information and digital age, and where they are planning on going - and where they could ultimately go.
This left me smiling at times, horrified at others (all those books), but as a whole it was heartwarming and uplifting.