Some of the features:
You can add clippings of text, images and links from web pages to your Google Notebook without ever leaving your browser window.
You can create multiple notebooks, divide them into sections, and drag-and-drop your notes to stay organized.
You can access your Google Notebooks from any computer by using your Google Accounts login.
You can share your Google Notebook with the world by making it public.
You can also find a full overview of the features.
There is a small file to download for IE or Firefox that allows you to open a mini notebook without leaving the page. I am not sure exactly how I will use this new Google product, but it seems to have a wide variety of uses.