I'm adding to to my (yet unpublished) list of books necessary for understanding WWII. It is the real story of the zookeeper in Warsaw Poland during the German occupation.
Diane Ackerman writes beautifully. If she decided to write the life-cycle of slugs, I'd read it and enjoy it; she is that talented. You may recognize her from A Natural History of the Senses.
She has carefully researched and documented the lives of Jan and his wife Antonina as they care for the animals, and later the people, that are in their care.
I find it fascinating that Diane Ackerman has not put words into her characters' mouths. In all cases, when a person in the story speaks, Diane has used documented quotes from letters, journals, and personal accounts. I can hardly fathom the work it took to rebuild the story from written archives and then to present it in such a readable manner.