The first e-book reader, the 1998 Rocket eBook, actually used a reflective LCD screen, similar to a calculator or an original Game Boy. The problem is that thes

The first e-book reader, the 1998 Rocket eBook, actually used a reflective LCD screen, similar to a calculator or an original Game Boy. The problem is that these screens are quite dark even in their monochromatic version (without subpixels). The reason is that LCDs require filters for polarized light, which block a large portion of the light even for "white" pixels. This is likely why the Rocket eBook failed. E-book readers only took off when Sony in 2006 introduced devices with an electrophoretic display made by E Ink, which had contrast approaching actual paper. But unfortunately that contrast only works when no color subpixels are involved. At the time quite a few other e-paper screen technologies popped up which had much faster response times than E Ink's electrophoresis displays (Liquavista, Mirasol) and some even had (in theory) better potential to make subpixel-free color screens possible. Unfortunately none of them could quite match the contrast (and perhaps price?) of E Ink's monochromatic screens. Which was fatal, as e-readers were the main application of those screens, and those really only require a black-and-white image. So the other technologies were abandoned.