I've had an e-ink device, and read ebooks on a number of devices. Some notes:
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If it's a casual read and I can get the book in epub or mobi format, I might just have it on my phone and use Librera.
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I did not like e-ink displays at all. The text itself doesn't appear easier on the eyes to me, and if anything the jarring refreshes on each page turn make the overall experience even more straining. For this reason regular Android tablets have become my preferred way to read books.
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For tablets I suggest one that is at least 10 inches. A lot of ebooks are still only available in pdf format, and I've found that anything smaller than a 10 inch display makes for bad pdf reading.
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Following from all that, I would suggest the Pixel Tablet, because from a privacy perspective, you have the option to install GrapheneOS on it. From there you can get F-Droid, install any of those ebook apps, and now you have a reasonably secure and private ebook reader - and the best part is, because it's a general purpose tablet, you're not accumulating unnecessary single-purpose devices. You never know if the tablet might have other important uses down the line.