My library is a bit of a mess after I was gone for a while...

I have returned to LibraryThing after a long absence. Before, I'd added almost a thousand books. I was meticulous in fixing the book names, including capitalization and punctuation, and making sure the right covers were always chosen, and uploading better ones as was needed.

It's been a few years, and upon my return, I find that the capitalization in many times is all wrong again, books are missing covers, or have wrong covers. I intended to add the few thousand books I still have yet to include on my LibraryThing library, but I'm not sure why this happened or how to prevent it. Is this a normal occurrence? I feel like I wasted hours and hours of work I now have to fix. I'm not sure if some error on my part caused it.

Are you pulling up the books in question from your library or searching them and finding the work page?
If you are on the work page, it will show the most common title for the book. If you are pulling it up from your library, it's how you left the book.

Did someone else have the password to access your library? If so, then they may have made changes you did not agree with.
If not, the library SHOULD be as you left it. No one can edit your library except you and who ever you gave the password to.

About the covers: If you are using Amazon covers and Amazon changes their cover, yours will change as well. So if you want to make sure that the covers don't change, use non-Amazon covers.

For the case - make sure you are looking at the book title (your data) and not the work title (the combined data). Your book titles should not have changed in any way or form - unless you adjusted a work title (via Canonical name) or were looking at them last time. If one of yours shifted, can you share an example so the engineers can try to see what may have happened.

You are mostly using Amazon covers. Member covers are reliable, Amazon covers aren't.

The same has happened to me. I have been adding books since 2009 and now I realise the information on the pages of my own books (not the book page) has changed over the years. Not only the covers, but also type of book (changed to ebook while I only have physical books), ISBN, even authors. All fields were changed here and there. It is very frustrating, and like Martha I was in the process of adding the rest of my library but now I wonder if there is any point in proceeding if the info I input (and that specifically refers to the books I own) is going to be changed to whatever editions are presently sold by amazon or to what libraries say. Is adding all books manually and not giving ISBN the only way to avoid this ?

>5 Estrela: As said already, no one except someone with your password can change your entries in any way. Only Amazon covers can change or disappear since those are not on LT and depend on Amazon itself.

If changing one Amazon cover to another, the system asks if you want to change the ISBN too, which is how those can change without you actually inputting another one in the field. As other edits, it also requires that someone is logged into your account, though.

If you imported a list of books through universal import and they had ISBNs, it searches and imports data from sources, rather than the rest of your columns, which is how you might end up with some values you wouldn't expect, but that would have happened at the time of the import, not years later. User data is sacrosanct on LT and no one can change it without logging into your account even if it's egregiously wrong, let alone without reason.

Edit: FWIW, you chart and graphs do not show any ebooks, just Paper Books and 153 with Media not set. Do you have an example where it says ebook in the catalogue? Perhaps there's some weird bug