Email comments: You can now have LibraryThing email you when people leave comments on your profile. Go to your profile and choose “edit profile” to enable this feature.

The profile now also allows you to choose whether to make your email public or not. Whether you make it public or not, I recommend everyone add an email, in case you lose your password.

Show number of copies: When looking at your catalog in list view, select “more options.” Not only does this add some buttons, including the delete button, as before. It now also lists by every book how many other users have it, as so:

You can click on the row-title “shared” to sort by this.

Recommendations: Book-by-book recommendations have improved again, with a lot of the pointless stuff removed. I also added a number by each book, showing the ratio of owners of both books to the owners of just the recommended book.

For example, here are the recommendations for Learning Perl. The 16/32 by the Perl Cookbook means that out of 32 copies of the Perl Cookbook, 16 are owned by people who also own Learning Perl.

I love how the blogosphere picks things up and runs with them. I asked for some feedback on the suggestions feature, and it became this independent meme. I particularly enjoy this submeme—listing all the books with little icons next to them—have it, don’t have it, good idea, bad idea, etc.

• AMVHoward on LiveJournal
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• New: Pralani

Are there any others to post here?

Book-by-book suggestions have improved.

Users with lots of duplicates—mostly from bad imports—were slanting things terribly. I knew this when my novelist wife’s books—hint! hint!—all came up with Spidering Hacks as the top suggestion. This came about because I have multiple copies of both her novels and Spidering Hacks, and do not represent their content. Screening out duplicates has also been applied to profiles. There are some other places where it needs to be applied. Duplicates will soon be a negligible issue. Hooray, I say.

Why are some rows yellow?

Users with duplicates will notice that some books show up with yellow rows. This is just temporary—in the future you will be able to either show the duplicates this way, show just the duplicates or ignore whether a book is a duplicate. It’s as far as I got: “Wallace and Gromit” trump feature addition, at least until later this evening!

I’ve added library suggestions for everyone as well as book recommendations for all books with three or more owners. Both are based on the same “people who own this also own that” algorithm. The library suggestion beta testers are split between those who thought it amazing and those who found it useless; it seems particularly good at guessing the second half of a partially-entered library. As for the book recommendations, I find them randomly either much better or much worse than Amazon’s.

Both features will get better as new books are added, but feedback is still much desired.

In other news, LibraryThing had graduated from the initial $10/lifetime plan. The new structure is $10 for a year’s membership and $25 for a lifetime membership. Those who have already paid their $10 were, of course, converted to “lifetime” status—my thanks for getting LibraryThing off the ground! This change will guarantee LibraryThing stays around for years to come.

PS: I made some final tweaks to the suggestion algorithm, and erased all the old reports. Incidentally, you may regenerate the report one per day. That gives me 24 hours to add that feature…

LibraryThing will go down for scheduled maintenance tonight at 1am Eastern time (6am GMT and, alas, 11pm in California). I expect it to be down for 2-3 hours.

Second, if you got this far, you’re in a very small minority of LibraryThing people—the cream of the cream, perhaps. So, here’s the scoop:

I’ve got an algorithm that tells you what books you “ought” to own. Basically, it looks at people who have similar books, and figures out what books they have that you don’t, adjusting for how close their library is to yours and for how common a given book is generally (the Harry Potter effect). If you want to look at your list, email me. NOTE: TELL ME YOUR USER NAME. I CAN’T READ MINDS!

The list is by email only for two reasons. First, it currently takes about five minutes to create, without breaking the server. (I’m taking the servers down tonight in part to speed such algorithms.) Second, I need feedback before I put the algorithm up.

It’s a lot harder to write a good library suggestion algorithm than I thought. If you like thinking about algorithms, this is an interesting one to think about.

The current algorithm has some flaws. First, it tells you about popular books you are actually avoiding. Thus, my brother isn’t a fan of Roger Zelaney, but his sci-fi heavy bookcase when matched to other sci-fi bookcases tells him he ought to own them. Second, it doesn’t think about different categories of books. Everyone’s library has more than one special section, but a “democratic” algorithm favors the largest section. So, I have a special interest in Greco-Roman divination, but it would never suggest books on that topic because my divination section is dwarfed by my other sections.

I have a number of other algorithms to look at. I’d like to test Dewey clusters (popular books in a Dewey-number range that you have a lot of books in), library suggestions that “bubble up” from book-by-book suggestions, and so forth. I’m not too interested in algorithms based on user ratings. My belief is that, in the aggregate, a library is a fair representation of a given person’s likes and dislikes. Even a “bad” book should inform the algorithm—people don’t buy books randomly.

The goal is to produce a better selection engine than Amazon has. Think big, I say.