I use Books
from Aetherial Software, not for the books I own, but to keep a running list of the half-dozen books I find in the bibliography of every book I read that I'd like
to read. I find out if they're in any of the four library systems I can use, and if they are, add them to the list. The list will of course grow and grow until I die, but it means I can always find something!
It can autofill publication data and cover art from the Library of Congress, The British Library, The University of Sydney, Amazon (USA, UK, & Japan,) Amicus (Canada,) Bibsys (Norway,) Det Koninglige Bibliothek, NCL Taiwan, The Royal Library of Sweden, SBN OPAC (Italy,) The National Library in Warsaw, & Vrije Universiteit Amsterdam. And it's free!
The only annoyance is that I have to keep two lists: One for Seattle and one for everybody else, since Seattle and King County use different call numbers for the same book a lot of the time, and there'd be too many dupes. I thought these things were supposed to be standardized!