A sub-compact laptop
made by Toshiba
weighing just a little over two pounds
-- about one kilogram
. Named for the Italian
word meaning small book. It's actually about the size of a VHS
The libretto features a very small 80% sized keyboard making it almost impossible to touch type on, and very difficult to even two-finger type on (unless you have small hands).
The libretto was first introduced in Japan, though US models are now available.
While it ships with a Microsoft Windows operating system, getting Linux on it is actually pretty easy -- the process is well documented online.
The latest generation of librettos contains a small webcam much like the Sony picturebook.