OK, so I got this pamphlet off a flatmate. I discovered that you can get copies off the WWW, here's a link:

http://www.abctruth.net/books/just-one-message.pdf

It's clearly some islamic witnessing materials. I brought this to the attention of some atheists, who promptly branded me a proselytising Muslim, which I didn't think was very nice. So I'll bring it before you guys.

In it, the author refers to the Old Testament, New Testament and Quran affirming that "The true God is only ONE. Worship him ALONE and keep His commandments." This is the main point of the pamphlet.

In it, there is a criticism of Christianity, in that he says "they [Christians] perceive this one God to include 1- God the Father 2- God the Son 3- God the Holy Spirit." He then claims that this contradicts scripture, citing John 5:37, 1 Timothy 6:16 and Exodus 33:20.

He "sincerely and honestly" asks "How can we reconcile the dogma that Jesus is God and the Biblical testimony that no one has ever seen God nor heard His voice?"

Basically it's an attack on the doctrine of the Trinity, which I never got either. I've heard some pretty outlandish explanations for it in the past, and I'm not particularly interested in another defense from anonymous netizens of same. I would be interested in what theologians have to say on the matter, and whether they can give a cogent response to such a challenge. So, any good references?