Books that are text only are ideal for E Ink displays, as this type of display provides the closest experience to printed paper available amongst all electronic devices. The E Ink contrast is poorer for other colors of “ink”, and therefore most E-Ink eReaders are black/grey on white. There are many books that are monochrome and text only, in fact text only books are the most common types of books that are bought or read.
So, the E-Ink display is best suited to display the most popular type of books: text only, non-interactive books, both fiction and non-fiction. But, additionally, some books with images in addition to text can also be displayed very well on E Ink ereaders provided that the images are monochrome or can be adequately rendered in monochrome. For these types of books, the main disadvantage of an E-Ink display, the low refresh rate, becomes irrelevant.
Furthermore text only books tend to be non-color, and this makes another disadvantage of E-Ink displays also irrelevant: poor contrast of color image on a color E-Ink display.
On the plus side, not only is the display readable outdoors, and less stressful on your eyes, but the resolution of all E-Ink readers is better than than most LCD displays (167 pixels per inch), and no worse than even the very best LCD displays available, although not a good quality printed text (300 pixels per inch).
LCD based ereaders outperform E Ink ereaders when the book contains color images or photographs, or has interactive content. Example of such books include children’s books, comics, and magazines. However, if your reading list is mainly text only, an E Ink ereader may be the best ereader for you.