I think my problem with Yashim was not that we didn't know much about him just yet, but that he had nothing personal at stake through the mystery. He was just doing his job. So I couldn't really feel for the guy or fear for him or root for him because there was nothing personal at stake for him.
I guess something about the initial description of Yashim and his early behavior convinced me that he is just a very service oriented individual (someone who gets personal enjoyment out of helping others.) Also, he was very clearly duty oriented and although it wasn't clear WHY he felt that it was his duty to meet with the seraskier in the first scene, it was clear that he felt it was important. Maybe I'm too easy to please...
If you liked the historical detail in The Janissary Tree, you may want to read Goodwin's Lords of the Horizons
, it is the same type of historical detail applied to history.
I haven't gotten to the Collaborator of Bethlehem
yet, but I'm still looking forward to it!