1. A method for facilitating computer-assisted comprehension of texts by a user of a data processing system, said method comprising: providing a digital representation of a text, the text including at least one occurrence of each one of a plurality of expressions, associating each expression with a difficulty index indicative of a corresponding comprehension difficulty, selecting a set of the expressions according to a comparison of the corresponding difficulty indexes with a threshold value, associating each selected expression with a corresponding explanation, and outputting at least part of the text with an indication of the explanation of each corresponding selected expression.