Ma'ariful Qur'an hasn't been written by Mufti Taqi Usmani Sahab, but rather by his father, Mufti Shafi' Usmani Sahab (rahimahullah). In its english translation, Mufti Taqi Usmani Sahab worked on the translation of the Qur'an into English, and thus the translation of the verses in the English translation of Ma'ariful Qur'an is by Mufti Taqi Usmani Sahab, while the rest of the work is by Mufti Shafi' Usmani Sahab. Later on, Mufti Taqi Usmani Sahab re-arranged his translation and published as a separate work. Anyway, let's see what Mufti Taqi Usmani Sahab himself points out regarding Qur'an translations: http://www.youtube.com/watch?v=9GaqDqp0Ruo