Change node title and node field content
I think the $node will be a object and not array. You are trying to access it like an array, hence you get php error.

function module_node_view($node, $view_mode, $langcode) {
  $node-&gt;title = 'TEST';
  $node-&gt;field_description[$node-&gt;language][0]['value'] = 'CONTENT';
}