In a three-page conclusion, Van Parijs sums up what he has been doing in his book, which is best said by himself (p. 207):

This book has attempted to address systematically the normative question of how our institutions should treat our languages. Its core idea is emphatically not that we should celebrate linguistic diversity as a value in itself which would be our duty to preserve or promote. Nor that we should endeavor to stretch the category of fundamental human rights so as to encompass some substantive linguistic rights. Instead, this book’s source of inspiration has been the widespread feeling that formal and informal linguistic regimes are sometimes very unjust in a number of distinct senses. And its main task has been to spell out the conceptions of justice that such feeling presuppose and to outline their practical implications.

His main conclusions are summed up as follows (208):

1. It is unfair that non-Anglophones should shoulder the whole burden of learning the lingua franca (English).

2. It is unfair that the growing currency acquired by their language should give anglophones multi-dimensional advantages. But this is bound to shrink and may reverse over time.

3. The most effective way of securing parity of esteem in the field of linguistic justice is granting each linguistic community the right to impose its language as the medium of instruction and public communication in some territory.

I think I need a few more days to make up my mind about my overall view/judgement on this book, but the comments section is open for anyone who has already done so.