Thank you for recommending this book! I actually have a trilobite fossil that I bought years ago as well and I kept pulling it out as I read this book.
What cool creatures they are with crystal eyes (calcite). I was absolutely amazed that they had found trilobite larvae fossils and enough of them to actually map their development to adulthood and also use the larval stage to show how some trilobites were closely related even though their adult bodies were markedly different.
It was a very interesting walk back in time.