As a child growing up, I used to read the encyclopedia at the breakfast table. and read under the covers with a flashlight. If you love books, you know the feeling. So it's easy to like a monk who gets caught reading a banned book in an outhouse at a monastery. Giordano Bruno is caught in an outhouse in Naples with a copy of Erasmus's Commentaries. Trapped, with nothing else to do, well, he throws the book "in". But it's not enough to save him, and the Inquisition is called for him. Making a rough & ready escape, he flees the monastic life and becomes something of a philosopher adventurer.
Eventually falling into the retinue of the French ambassador to England, he finds himself in England in the circle of Walsingham, Queen Elizabeth's secretary of state, and chief spyhunter. Giordano finds himself embroiled in a murder mystery as well a secret community of Catholics, who are under edict.
Giordano is an historical figure, who extended the Copernican theory of the relationship between the Earth and the Sun to the rest of the universe, accurately theorizing that the stars were other Suns. For this he was indeed accused of Heresy, and [Heresy] seems quite true to actual events, although of course many of the events and people are likely invented (such as Sophia, the attractive daughter of Underhill the Rector). Underhill himself is historical and did debate Bruno at Oxford.
Heresy is the 2nd Medieval/Elizabethan novel I've read recently about a male protagist/detective, written by a female novelist - Veil of Lies by Westerson (http://www.librarything.com/work/6352302) is the other. Readers of one will like the other. I think Westerson does a better job of handling relationships; Giordano's interactions with Sophia seem forced and superficial to me. But Parris's depictions of the forces of religious, cultural and political conflict between Catholics and the supporters of the Elizabeth are sharp and bring home the reality of the era. Heresy is well written for a first novel, moves quickly, and doesn't flag. Fans of period history will enjoy it. In spite of Bruno's known interests in arcana, magic, astronomy and memory tricks, this is no "Name of the Rose". Just a well-written, enjoyable read.
(Received through the wonderful LibraryThing Early Reviewers Program)