I looked at all three. I found Booktagger slow and a little clunky, but I like the blog, especially the outfit called The naughty librarian costume from Target. I noticed that the Booktagger website is not well developed. The Discussion page shows all activities by all users which might be a privacy concern or too much information.
I joined LibraryThing a long time ago, but haven’t used it much, since 2007 it did not changed from my point on view. I was pleasantly surprised that books I have added 2 years ago were still there and number of people who have the same books has increased.
Then I signed in to Google Books, went to My library and found some books and added them to my shelf. The idea of saving a list of books read, be able to find them online, read part of them is a good, in my point of view, for reader/ librarian in making a decision before purchase.
If I have more time, I would like to return to Google Books for further explorations.
I checked the Google Books Library Partner page to see what libraries do with Google Books; they create their digital collections and open it to the World. I visited University of Wisconsin – Madison Google Digitization Initiative, and checked http://www.news.wisc.edu/newsphotos/libraryGoogle.html. Image of Vacuum Milker (U.S. Patent, 1868) caught my attention. The 2 questions I would like have an answer for – about copyright and how expensive these projects could be for universities.