I'd just like to add a bit to this. The notes above are not bad, but somewhat generic - remember that you MUST pull examples from the text and state why they were used.
For example:
Why is Ondaatje constructing an "unofficial history"? This is pretty obvious, but cover all corners.
Now about the text referring to itself as artificial and constructed - you can go into this a LOT more. Now, everyone studying this text LOOK HERE AND READ THIS BIT. I don't spoon feed, but I will give a hint - Alice says somewhere that "You reach people through metaphor". Provided someone actually responds, this can go into a discussion about metaphor (VERY VERY VERY IMPORTANT!!!). But to continue with other things I think are important to add:
The lyrical prose is more than just pretty. Have a look at some creation myths one day. They're also written quite prettily. Why so? What is the effect of this?
Ah, and now there is intertextuality. Currently doing a bit of this in Uni. Intertextuality is really great - provided the reader actually knows what you're quoting or referring to, it can open up doors for entirely different meanings - or add depth to the meaning already presented (eg "walking away from his house, he knew exactly how Adam must have felt when he left Eden". Lame example, but you get what I mean). This also links with metaphor, but I'll wait for some more responses before I go into that further - it is really really something you need to work out for yourselves to get the full effect, but I'm here to nudge the process slightly
Mini-narratives can be linked to metaphor
Lack of reality also to be linked to metaphor
Ooh! ok so there is some metaphor in this thing. Something that can be added - there's a line like "the puppet was brought before the authorities, unable to speak a word" which would be GREAT.
Final note with the essay - please underline your texts!