Giordano Bruno, 1548-1600, was persecuted by the Church for his heretical views, most notably his belief that there are countless inhabited worlds around distant stars. Bruno also advocated the Copernican system. Unlike Galileo, who grudgingly recanted his views, Bruno ended up being burned at the stake.
The Heroic Enthusiasts. (Gli Eroici Furori) L. Williams, tr. [1887 and 1889]
The introduction to this translation of one of Bruno's most celebrated (and cryptic) works has a good biography of Bruno.
A more recent translation of Gli Eroici Furori can be found at the Esoteric Archives, as well as some more texts by Bruno in the original Latin. [External Site].
Giordano Bruno, His Life and Thought, with an Annotated Translation of His Work 'On the Infinite Universe and Worlds' by Dorothea Waley Singer  [External Site]
Also available at Amazon.com:
The Ash Wednesday Supper
Giordano Bruno and the Hermetic Tradition, by Frances Amelia Yates