His other legacy.
I've read literally dozens of books about Charles Darwin. In most of them, his children, if they're mentioned at all, hover in the wings somewhere. Tim Berra's book puts them centre-stage. Each of Charles and Emma Darwin & His Children get their own chapter.
Many people will know the story of Darwin's favourite child, Annie, who died when she was 10 years old. To some extent, Annie's story has eclipsed those of her siblings. In reading this book, I was delighted to make better acquaintance with his other children—especially Henrietta (who effectively became her father's editor), Francis (who became his father's lab assistant and secretary), and George (who became a world-class geophysicist).
The fact that the Darwins had no less than ten children means that some of Tim Berra's potted biographies are necessarily brief, but they contain enough information and interesting snippets for most casual readers—and enough to whet the appetites of us serious Darwin groupies.
Definitely one for your Darwin library.
Disclosure: I received a free review copy of this book from the publishers.