The Diggers Movement in the aftermath of the English Civil War tends to be forgotten, along with the Levelers (also in this series) with most historical focus on Cromwell's rise to power. While this book is not in anyway a history of the Diggers, it presents a collection of their pamphlets.
This collection of documents by Winstanley, including the important A Declaration from the Poor oppressed People of England, shows that modern socialism and democratic egalitarianism was not born in the salons of Paris but in the fields of England. With an excellent introduction by Tony Benn this is a must have for students of history and politics of the left.
My only criticism and warning is that, if like me, you are dyslexic or have nightmares brought on by GCSE Shakespeare classes you'll find the 17th century English somewhat of a hassle. If this is likely to cause bother I suggest looking for a copy in Modern English but otherwise go for this and enjoy.