Flesh and Fire follows the story of Jerzy, a slave who becomes an apprentice Vineart. A Vineart is a magician who grows the grapes which make magic wine - an original and well-described magic system which is much more interesting than I can make it sound in this review. But the Vinearts of the world are coming under covert attack from an unknown enemy. Poor Jerzy has to help his master investigate the attacks, ultimately being sent on a spy mission to a foreign city - all while he's much too young and inexperienced.
I liked the writing and the development of Jerzy as a character. World-building other than the magic system was relatively limited, effectively growing with Jerzy's education, so the reader is not overwhelmed with strange names too early. I suspect we will see more of the world in the next book.
To the reviewers complaining that the book is unfinished: stop whining! The book clearly says it's book one. You know there are going to be more books. If you don't like unfinished series, why not just wait for the Ms Gilman to publish the next books instead of cluttering up everyone else's reviews? I actually liked the ending - without spoiling it, I can say that there is resolution of one sub-plot, and the plot in book two is clearly about to go off in a new direction.