There are a number of other books and writers who have been particularly important to me, or which stand out as texts by which to get your bearings.
Soil and Soul (2001), by the Scottish activist and visionary Alastair McIntosh, is the only book which I have finished and immediately sat down to write to the author. It is a powerful account of the campaigns for Land Reform in Scotland, the Isle of Eigg buy-out and the drawn-out battle to prevent the Roineabhal superquarry on the Isle of Harris. It's also full of wisdom and sanity about how to be an activist without burning out, not least the wisdom of "wu wei" - doing through not doing.
The Spell of the Sensuous (1997) by David Abram is a remarkable weaving together of anthropology, ecology and philosophy. There are few writers with whom I feel more common ground.
The novels of Aidan Chambers' Dance Sequence were hugely important to me in my teens. They explore the turning points of a particular kind of late adolescence - and, for me, they served as a kind of emergency orientation kit before I had found the rest of the writers listed here and begun to build maps of my own.
Lee Hoinacki was Illich's longest-standing friend. His Stumbling Toward Justice: Stories of Place is a wonderfully unruly sort of autobiography and a lesson in how to live well. It is like hearing the other, earthier end of a long conversation which is both strange and familiar to readers of Illich.