This is a tale with two threads: a Ghosh-like doctoral student traipsing around rural Egypt and west-coast India in the 1980s, and a fictionalised reassembly of the lives of some marginalised characters from the great trading days of about a millenia ago, which appears to be the focus the student's research. Ghosh wonders how much of their lives he can reconstruct, for the figures of history are usually those who have the education, money and power to inscribe themselves on it. Of course what he in fact does is reconstruct their lives through an educated, cashed up and powerful trader who exchanged many letters with his overseas partners and family. The story of how those documents came to be preserved is quite fascinating, but is not teased out enough here. (That would make a great story, the intrigues of colonial times and the tastiest material in the Geniza. Surely someone's done that already.)
There's lots of old Judaic stuff in this book, too much for this non-specialist to really appreciate. There's also a lot of stuff in general that is difficult to appreciate, especially given the apparently low standards and availability of evidence in this scholarly discipline. The present-day stuff is mildly entertaining in the way of all well-told travel stories, but is not spectacularly distinguished. One grows tired of Amitab growing tired of having to be all of India in one man to a provincial community of Egyptians.
Why the interest in the slave anyway? We really only get one detailed event in his life, viz getting turpsed up in Aden.