Excellent start - I was gripped from the beginning! Desolate and hopeless, your prose really speaks volumes without resorting to the 'I felt angry' type sentences.

The only thing I would disagree with is where you address the reader personally in the Prologue and talk about why you are writing the manuscript. The content around these 2 paragraphs is so gripping - why break up the flow for something you could put at the end/elsewhere? I would maybe develop the character of Marco before the Janissaries burst in too; you have the action & confusion of the desert slaves, then too brief a pause of peace before the jannissaries come in. I felt like it moved too fast - maybe develop the 3 characters we meet just slightly more? Though I do see you plan to do it as a gradual process throughout your novel.

Love the idea - I will keep reading!
Luv K x