You can construct a popup like that very easily using a regular div
element and some CSS. In particular, the position: fixed
CSS property will let you put something at a position on the window, no matter how it scrolls.
Here is a simple JSFiddle that demonstrates the technique: http://jsfiddle.net/BinaryMuse/ndr2Q/
You can click the titles of the books to expand their description, which will hopefully make the preview window tall enough to scroll. (If not, just resize the window.) No matter where in the document you scroll, the "popup" window (which is just a regular element with an ng-show
and some CSS) stays at the bottom-right of the screen.
You can find libraries, like Bootstrap, that present jQuery plugins to allow you to do popups on the page, but in general they're designed to prevent the user from interacting with the page behind the modal in any useful way. A technique like this allows you to scroll around and use the page in the background similar to Gmail's interface.