As stated in the "Buy book" button - the latter link is an eBook (for some devices), whilst the former is paperback and download (for all devices). There is no real descriptive difference between them, except the former will only work on some devices (of which I know not).
There was a discount for the second edition, probably around 2 to 3 months ago

The list of changes is too extensive to list, but incorporates all the new webOS and Android stuff...