If you are not up on the issues, you might read:
https://wiki.mobileread.com/wiki/Choo...n_Ebook_Reader
If you aren't worried about DRM, then a cheap choice is:
https://wiki.mobileread.com/wiki/JetBook
One really, bad idea, but it would work. You can purchase a used Palm device. I did this for a few months when I was waiting for a new reader to hit the market. I got a nice Palm TX for about $70. However, I think the technology is ready now, and I would go for a dedicated ereader.
If you have a little more, I would go for the Astak EZReader from Fry's. It is eInk based.
For those who aren't constrained by budgets the choice is usually between Sony and Amazon. The Sony has better support for organization (folders). The Amazon Kindle is US only for now. The Kindle's strength is the ease of buying and downloading books wirelessly and the ability to synch books between the Kindle and a iPhone.