I use "LibraryThing" LibraryThing | Catalog your books online | LibraryThing to catalog my books. One cheat I like is the ability to import an entry from another user into my page. Been using it for years, never a problem. And I have no financial interest in the site. This is my file: Larry_Jewell | LibraryThing | LibraryThing
Oh, there's a small fee ($25 or so) for over 100. I've already paid that. /hint And you can enter the UIC code number and the software will fill in the blanks.
Just the one time when I paid it. Consult the admin there for current practices. Lots of room, my wife listed 800+ books on her page.
Private to all but the prying eyes of the En-Ess-A. Actually the software is probably very useful and like others here, I have thousands of books.
When I showed this site to my wife I didn't hear a peep out of her for three days. There might have been a downside as well, didn't see one.
On a related note, I'm assembling my collection of books along with a physical card catalog. I'm currently deciding between dewy decimal and Library of Congress. The more I research the more I'm leaning toward Dewey.
I don't know of Librarything pulls the info when you enter the Dewey #. I've been using Congressional since the late '80s. ALL the university libraries I used to visit were Congressional.