Nevermore is much better in concept than in execution, sadly: 24 species whose extinction was caused by humans, described in contemporary observations prior to extinction, modern scientific knowledge of the species where it exists, a beautiful illustration of what the animal looked like, and a poem about it by the author.
The illustrations were lovely and the contemporary observations were fascinating, but the poems just didn't do it for me. I think it must be hard to create 24 compelling literary works of art on essentially the same theme for a single volume; most of them ended up feeling forced to me.
However, I think the book accomplishes the author's primary aim of creating sympathy and grief for all of these vanished creatures, and reducing sympathy for the human slaughterers. It is very difficult to retain one's admiration for humanity when, over and over, the contemporary accounts of the species and their extinction are, "We found a new country with uncountable numbers of these animals, so innocent and unwary of us that they didn't know to run away, so of course we killed them all for fun."