Here are my opinion and warning for these device and explaining for who this device is, and for who it is not 

This device has 2 massive problems. No frontlight, so can't use in dark, and you get this effect that you can see on the pictures when reading in direct sunlight. 

I have owned other e-ink devices and I have not seen such bad case of bleaching. It's gone the moment you refresh the page under shadow but it's hella annoying. And keep in mind that this is with 1 page refresh, with 5 or higher it just bleaches the page further and further. "Dark mode"  is no better just a lot of ghosting. So it definitely lowers the experience 

I have tried stock firmware, cross point and crossink, none make it better. 

Something I noticed is that whenever it loads a page, it renders it, and then renders it again with lower quality then the initial render(this being under shadow where I get best quality of text)

Personally I love the device, but it's for very specific people who want something cheap and that they can carry everywhere with them and put in a pocket, key chain or whatnot. 

I mainly got it to test the size, since I intend to buy a eink from haisense, boox or bigme in a phone size, but just was not sure if the size will be enough, so I went with smaller device and I have been doing almost all my reading on it, but it definitely is a turnoff whenever it does that under sunlight, and that's also the main reason of buying it for me. "No blue light, pocketable reading device" 

Technically u can read manga on it if u have good vision as well. But at this point if your whole idea is just to read more outside, while not really the best solution or experience, matte screen protector does about the same job. 

I hope in future versions they improve on screen quality, and also have bigger screen something in the 5-6 inch size while still pocketable. The idea is there, and there is massive following, but the execution is not there. Perfect device for its price, but I am all in for paying extra for better quality. So I might just wait for haisense a10 or palma 3. Or in the end of the day get high quality screen protector for my daily phone. 

I really wish that we could get a premium, fully security supported eink phone that I can put my mankings and all with peace of mind but as of now thats also not an option. I feel like the whole small e-ink market is quite complicated

Fair warning for use cases of xteink x4