Like most new sources with this much information, my initial impression is to feel overwhelmed. But inevitably you find a way in. I found it through the "Statistics" portion of the website. I'd already added in four books and from the statistics page I clicked on the "Characters" link on the Common Knowledge tab on the left. This brought up links to characters in the books that I'd added. You can do several things, one of which is to find similar characters in other books. Honestly, not so impressed with what I found. Nor am I eager to catalog the books of my collection, and navigating the various avenues of bookdom, I'll take Amazon, thanks.
Still, there are cool things with websites like this. I was down on LibraryThing until I searched a few books that I genuinely love and I found a few people who feel similarly about those books. I can't exactly put my finger on why it feels different reading those comments about the books as opposed to reading comments on Amazon. The interface of LibraryThing just feels much more grassrootsy, "lo-fi" to use music terms.
Like all new resources, it seems, it's important to get over the initial pessimism or cynicism about how they can be useful. I won't take all of these tools with me, but I might adopt a few of them. I hope I give them a shot.
8 years ago