The Armenian Genocide by Raymond Kevorkian would be a good book for him to look into. Fairly comprehensive look at the genocide, and also well regarded as far as I'm aware. "English Historical Review" gives a pretty favorable review, noting that it "comes closest to providing a complete history" and "very ably contextualized the genocide within a wider political, social, and economic framework". Definitely the book they want.

I would also recommend "Children of Armenia" by Michael Bobelian. It doesn't concentrate too much on the genocide itself, which only takes up the first section of the book, but mostly focuses on the memory of the genocide, both within the Armenian communities and outside it. It isn't particularly academic, but worth picking up.

There is also "Operation Nemesis" by Eric Bogosian, which is a bit of a pop history, and covers the assassination campaign launched by Armenian nationalists against various Ottoman officials who they held responsible for the killings.