I bought a BeBook ereader some years back from an ebay seller, not easy to find the BeBook or similar like Jinke, that support many, many formats. The BeBook seems to maintain some structure, with various choices in the menus of how to display the lists. It is all button navigation, no touchscreen. I was looking specifically for an ereader for my large collection of .lit ebooks, which Microsoft strangely stopped supporting. Their support ended after Windows Mobile 6.5, I believe. My first Windows 7 phone didn't have it, and Microsoft support told me they wouldn't be creating anything like the old Microsoft Reader software for it. I did discover that Calibre reader on my Windows computer will open .lit, and many other formats of course. The BeBook is not touchscreen, but is very lightweight, really long battery life, and can be read in bright sunlight, but no backlight to read in lowlight situations. It works great on a small plastic tilt stand like a Case Logic one, preventing nose injuries from falling asleep reading. I Velcroed my ereader to the stand, since there are no clips to hold the gadget on the stand. The other ereaders that are very capable of reading a huge number of formats, like the Jinke, can hardly ever be found. There is a good Wiki that has several tables showing device features.
https://en.wikipedia.org/wiki/Compar...e-book_readers
But maybe better than a dedicated ebook reader would be an Android device, that could be upgraded as needed over time, since the Playstore has a Calibre version, and maybe it would allow searching and organizing like the Windows based one. I guess if you have added genre tags via "master" Calibre tool, those tags would transfer to the gadget if you use Calibre's tools to send ebooks to the gadget, which could then be used by reader software on the Android device. But I am a novice at that, sorry. I just recently saw that Calibre was in the Playstore. I would expect that it might exceed the capacity/capabilities of most any Android ereader software, including Calibre, to quickly display thousands of ebooks, since the working memory on most of the gadgets don't have a huge amount of memory-RAM. My 30k of Kindle books won't display on most Android devices, since the Kindle app seems to download a cover for each one, using up a lot of space, and whatever RAM is needed.