Find the ISBN number of the book whose cover you wish to embed into a Web page. You can find a book's ISBN number on its back cover or with the publishing information in the front matter. Alternatively, you can find a specific ISBN by using one of several online search tools.
Visit the LibraryThing website and note your API developer key. If you don't already have a LibraryThing API developer key, click on "Register now" and follow the onscreen instructions to create one.
Launch Notepad or a text editor or Web editor of your choice. Open the HTML file that contains the source code of the Web page into which you wish to embed the book cover.
Type or copy-and-paste the following code into the file, replacing "YOURKEY" with your alphanumerical API developer key and the uppercase "ISBN" with the ISBN number of the book. Do not replace the lowercase "isbn" directory name in the code.
<img src="http://covers.librarything.com/devkey/YOURKEY/medium/isbn/ISBN">
Save the file and upload it to your Web server by using your host's upload tool or an FTP client of your choice.