I am looking to buy an eBook reader. Can any one suggest which one is good and where can I buy this in Karachi.
Ebook readers right now are a novelty and are pretty expensive. The best ones are Amazon Kindle and Sony's line of ebook readers. A number of other company's are launching their products in the coming months such as Plastic Logic. I recommend you wait another 1-2 years for the prices to come down, bugs to be fixed in the current e-readers and the variety in brands to increase.
I think you are right; I have to wait as these gadgets are very expensive and on top of it I can not fine Kindle or Sony PRS series in Karachi.