'best' is a tricky adjective to satisfy. I have a Pocketbook HD3 Touch, and really like it. It's a 6" monochrome model, with white-to-red-tint backlight. Pre

'best' is a tricky adjective to satisfy. I have a Pocketbook HD3 Touch, and really like it. It's a 6" monochrome model, with white-to-red-tint backlight. Previously I owned their 360 model - with a clip-on cover and at 5" size, it was perfect to slip into a jacket pocket for bag-less outings. Sadly ebooks in that size are rare now. Pocketbook are known for supporting lots of formats of ebooks, and being 'pretty open', but your expectations will vary there, I'm sure. They did bring out a similarly sized colour eink model about 2 years ago which looked tempting, though I personally don't have much material in that size that'd benefit from colour, and moving around text book, let alone A4 sized material on a 6" screen would be awful.