Help my brother source some books

So my brother Screwy is a philosopher. This means he occasionally gets people who want him to help with their philosophical problems. Not quite as bad as admitting that you're a doctor during social occasions, but still.

In this case, he's passed a request on to me, because he thinks that I know more SF/F readers than he does. The issue is as follows:

[My interlocutor] is writing a fantasy novel. He asked me to read the bit he has written. It is much as you might expect. Anyway, one interesting feature of the story is that there is this group of lizardmen who seem to have a religion that revolves around doing evil in the full knowledge of its being evil. I pushed him a bit on this because I thought it was a) interesting and b) badly executed. He suggested that it was because I did not grasp the effect of their cold blood on their mentality. I suggested it did not come through in the writing and that he should have a look at other fantasy writers who try to create a universe where human logic does not apply and see how they handle it and also fantasy writers who create alien mentalities. The best I could think of, being the only fantasy writer I have read, was Tolkien and his Elves. I thought he did a reasonable job of creating a species who were minded differently from humans. He certainly does not provide an example of a universe with a logic radically different from our own.

I have a feeling that this question is going to be better addressed by SF than fantasy, but I'm not sure how picky Screwy's friend is about the distinction. Anyway, does anyone have any good suggestions of books that deal with convincingly non-human approaches to morality?