He has made some mistakes in his translation of the scientific verses of the Qur'aan, but in some cases is even better than Maurice Bucaille's. This book need to be read in conjuction with "The principles of state and government in Islam", to get a better understanding of Islam, by Muslims and non Muslims.
In my view, Muhammad Asad in his greatest work, Message of the Qur'an, has undoubtedly presented the most encyclopedic interpretation of Islam's Holy Book in print, supported by the most comprehensive footnotes to date. The author obviously carried out massive historical research of the classical scholars, and his interpretation brought a freshness to an ancient text that compels the reader to read on, and on, and on ....!
As a true scholar, whenever and wherever he differed from traditional orthodoxy, he clearly articulated his reasons for doing so. And this, in my view, has added authenticity to his magnus opus.
A word of caution to unwary: Unlike Pickthall, Asad's Translation is not literal but interpretative, a literary technique that explains the text to the reader from the translator's point of view, as is generally the case. Asad's English is also decidedly tough (unlike Dawood's). When reading Asad, one must master his complex construction.
One clear weakness in this book, however, is the absence of an index of any kind, which when added, would make the Message truly complete and encyclopedic in scope. Another point to be noted here is that Asad has studied the writings of the late Lahori Scholar, Maulana Muhammad Ali; hence, it is no surprise that the two hold almost identical views on many of the polemic issues associated with the Noble Qur'an, including the so-called theory of Abrogation (al nasikh wal mansukh), Jesus' Second Coming, Dress Code, Sexual Relations with those whom the right hand possessed, penalty for adultery, equality between men and women, immaculate conception of Jesus, among others.
This book should be bought and kept as a collector's item by the layman as well as the serious student of the faith. I sincerely recommend it.