eInk readers are perfect for linear reading, such as fiction / non-fiction / stories / etc. I do all of my leisure reading (i.e. fiction) on either my Sony reader or on my 10" tablet. But they are not so good for reference works where you need to flip pages a lot or deal with lots of diagrams.
Reference works, such as books on technical topics, I usually resort to reading them on the 27" display on my desktop (although some are passable on a 10" tablet). The main reason I buy those in electronic from is for search and space savings on my bookshelf.