I have an iPad, and it's not an option if you're reading that much! After reading 20-25 page on the iPad I also get headache and my eyes start to feel very dry.
I also had an eBook reader, the Sony PRS-505, it was ok as long as you have the ebooks in the .rtf format, because in that case you can zoom if you need to. Reading PDF file was a pain in the ass sometimes, sometimes the text was so small, that I prefered to read it on the PC or print it.
In my opinion the best solution is still pro buy a book or to print the ebook, for me there is still nothing comparable.