How big are the books? How many books are there in those 250 GB?
A typical size of a epub book, in my library, is a few 100 KB. Maybe 200 - 300 KB. If there are images or fonts embedded that may increase to a few MB. 1-4 MB.
PDF:s with a lot of images, like magazines, can be a few 10 MB. Maybe 15 - 30 MB. PDF:s consisting of mainly scanned images can be bigger still.
Since you have scanned the books yourself, I assume that they can either be fully OCR:ed, and comparable in size to a small epub, or depending on the images and format, very big.
I have my entire library of around 3800 ebooks, a mix of epub novels and PDF textbooks and documents, available on my Android tablet, using less than 10 GB. And the library is easily accessible using the metadata stored in the books. Metadata that I have modified and normalized using Calibre. I expect that the library can keep growing, but that I will be able to buy new reading devices with bigger capacities faster than my library grows. Currently I have 32 GB storage available on my device. In practice maybe 20 GB considering other uses. So my current library could grow at least twice as big using my current hardware.
No silly "A novel" or series information in the title of a novel. Series information goes in the series fields, and also in the filename to allow duplicates of books that are part of more than one series. All authors in the form LN, FN. And no different variants with or without initials or punctuation in the names. All books in a series use the exact same name of the series. All books by the same author have the exact same spelling of the name of the author. Books that are part of more than one series are typically duplicated. All of this was easy to fix using Calibre.
My books are also stored on my Android device in 54 different folders, loosely based on subject and language. I have all books on computer languages in one folder. Linux books in one. Historical crime novels in one, alternative history SF in one, and so on. I sometimes refine this when I think there is too many or too few books in each folder. Easy to do using Calibre. I just modify a field, and when the books are saved to device, from calibre, they are automatically grouped in different folders.
Since the metadata is normalized I can use my reading app to group books for instance by genre, author, title, series or folder.
If I decide that some other structure is needed, for instance group books by author inside each genre, or by genre under each author, or in folders based on series, that can be easily and quickly done by changing the save template in calibre and sending the books again.
Since the books have tags, and the reading app I use allow me to search using the tags, I can easily find books with special content, if I have tagged them. For instance prehistory books can belocated by searching in the folder "prehistory". Or "ancient Rome". Or "aliens". Or "supernatural". Or "Standard Library". Or "Cats". Or "Read!". Or other things that I have tagged for in order to help find books. I use calibre to maintain, remove, modify, normalize and add tags. Never ending job, but makes finding specific books very easy, both in calibre and on my reading device. For instance books that I am especially curious about and want to read soon. Too many of those...
