Almost any book not printed in or by people from Turkey, Pakistan, or the central Asian republics between the two.

The Armenian genocide isn't really "political" and there aren't really "sides" to take, in any meaningful sense. It happened, and the academic consensus on that fact is overwhelming; as close to unanimous as academia can be.

Especially in 2019, people who deny the genocide are almost without exception Turkish nationalists or their agents. People who are ambivalent simply don't care about the truth more than they value cooperation with Turkey for either business or geopolitical reasons.

This sounds paranoid, but it's difficult to describe just how badly the Turkish government wants to cover up the genocide; even though it occurred a century ago and was orchestrated by an entirely different government; the old Ottoman state. Turkey has spent, and still spends, millions of dollars lobbying the US government to refuse to label the event a genocide; as Turkey is a key NATO member, the US has so far always obliged. The Anti-Defamation League just finally came out against the genocide's denial in 2016, after years of accepting Turkish (and a few other governments) pressure.

Again, this is for political expediency--there is almost no doubt about the facts of the genocide among anyone who isn't either paid for their doubts or a Turkish nationalist.

Pardon if I seem to be challenging the question rather than answering it, but I consider this vital. It's almost unethical to act as if there are "sides" in this story, or there needs to be "neutral" sources. That horribly characterizes the entire history of the genocide. This isn't complex or he-said-she-said. There was a genocide that killed entire towns of Armenians, as well as Greeks and other undesired groups. It's quite well-documented. And there has been a decades-long campaign by one government in particular to muddy the waters around the issue. I'm in no way anti-Turkish, but the whole thing is extremely detestable.