Clearly extension on Firefox also grabs the text from 'next' page(s) content into the readable view. The built-in reader in Firefox can not do that. It is a very useful feature to have.

edit: While looking for the addon at addons.mozilla, I find that it has been discontinued by Evernote: 'This add-on has been removed by its author.' https://addons.mozilla.org/en-GB/firefox/addon/clearly/

Anyone know of another addon that works similarly?