There is a notion, popular among some conservationists, that we are living in the Anthropocene and should just go with it, embrace our species' role as master and gardener of all creation, and dispatch the idea of protecting wilderness -- untrammeled nature -- for its own or our own sake. Protecting the Wild is a response to that resignation and a positive case for continuing to protect wild places and restore ourselves in the process. (That's my summary, not the editors'.)
I highly recommend reading the whole book, which has many essays by actual writers. but if you'd like a taste, you can read my contribution, "The Humbling Power of Wilderness," adapted from a talk last fall at the Wilderness Act's 5oth anniversary conference.