The Syro-Aramaic Reading of the Koran

The Syro-Aramaic Reading of the Koran: A Contribution to the Decoding of the Language of the Koran is an English-language edition (2007) of "Die syro-aramäische Lesart des Koran: Ein Beitrag zur Entschlüsselung der Koransprache" (2000) by Christoph Luxenberg.
The book received considerable attention from the popular press in North America and Europe at its release, perhaps in large part to its argument that the Quranic term "Houri" refers not to beautiful virgins in paradise (Jannah), but to grapes there.
The thesis of the book is that the text of the Quran was substantially derived from Syriac Christian liturgy, arguing that many "obscure" portions become clear when they are back-translated and interpreted as Syriacisms. While there is a scholarly consensus that the language of the Quran is influenced by Syro-Aramaic, Luxenberg's thesis goes beyond mainstream scholarly consensus and was widely received with skepticism in reviews.
Thesis.
The work advances the thesis that critical sections of the Quran have been misread by generations of readers and Muslim and Western scholars, who consider Classical Arabic the language of the Quran. Luxenberg's analysis suggests that the prevalent Syro-Aramaic language up to the seventh century formed a stronger etymological basis for its meaning.
A notable trait of early written Arabic was that it lacked vowel signs and diacritics which would later distinguish e.g. ب, ت, ن, ي, and thus was prone to mispronunciation. Arabic diacritics were added around the turn of the eighth century on orders of al-Hajjaj ibn Yusuf, governor of Iraq (694–714)..
Luxenberg claimed that the Quran "contains much ambiguous and even inexplicable language." He asserts that even Muslim scholars find some passages difficult to parse and have written reams of Quranic commentary attempting to explain these passages. However, the assumption behind their endeavours has always been, according to him, that any difficult passage is true, meaningful, and pure Arabic, and that it can be deciphered with the tools of traditional Muslim scholarship. Luxenberg accuses Western academic scholars of the Qur'an of taking a timid and imitative approach, relying too heavily on the work of Muslim scholars.
Luxenberg argues that the Quran was not originally written exclusively in Arabic but in a mixture with Syriac, the dominant spoken and written language in the Arabian peninsula through the eighth century.
Luxenberg remarked that scholars must start afresh, ignore the old Islamic commentaries, and use only the latest in linguistic and historical methods. Hence, if a particular Quranic word or phrase seems "meaningless" in Arabic, or can be given meaning only by tortuous conjectures, it makes sense – he argues – to look to Syriac as well as Arabic.
Luxenberg also argues that the Quran is based on earlier texts, namely Syriac lectionaries used in Christian churches of Syria, and that it was the work of several generations who adapted these texts into the Quran as known today.
His proposed methodology.
"Plausibility", "judging" and "making sense" of single word involves looking at occurrences of the same word in more obvious Quranic passages, and looking at Aramaic apocryphal and liturgical texts, which were carried over almost verbatim into the Quran.
Word analysis.
Quran.
According to Luxenberg, the word "qur'an" ("reading, lectionary") is a rendition of the Aramaic word "qeryan-a", a book of liturgical readings, i.e. the term for a Syriac lectionary, with hymns and Biblical extracts, created for use in Christian services. 
Luxenberg cites the suggestion by Theodor Nöldeke "that the term "Qorān" is not an inner-Arabic development out of the synonymous infinitive, but a borrowing from that Syriac word with a simultaneous assimilation of the type "fuʿlān"."
Huri.
The word houri, universally interpreted by scholars as "white-eyed virgins" (who will serve the faithful in Paradise; Qur'an 44:54, 52:20, 55:72, 56:22) means, according to Luxenberg, "white grapes or raisins". He says that many Christian descriptions of Paradise describe it as abounding in pure white grapes. This sparked much ridicule and insult from the Western press who allege that "suicide bombers would be expecting beautiful women and getting grapes."
Khātam.
The passage in surat al-Ahzab that has usually been translated as "seal of the prophets" means, according to Luxenberg, "witness". By this reading, Muhammad is not the last of the prophets, but a witness to those prophets who came before him.
Ibrahim's sacrifice.
The verse 37:103, considered to be about Ibrahim's sacrifice of his son, reads when translated into English from Arabic, "And when they had both submitted and he put him down upon his forehead". But using Syriac instead of Arabic for almost the same Arabic "rasm", "he put him down upon his forehead", changes the meaning to "he tied him to the firewood".
Aya analysis.
The Quranic passage in surat an-Nur, 31 is traditionally translated as saying that women "should draw their veils over their bosoms" (Abdullah Yusuf Ali's translation, ""). It has been interpreted as a command for women to cover themselves, and is used in support of hijab. In Luxenberg's Syro-Aramaic reading, the verse instead commands women to "snap their belts around their waists." Luxenberg argues that this is a much more plausible reading than the Arabic one. The belt was a sign of chastity in the Christian world. Also, Jesus puts on an apron (Greek λέντιον, "lention") before he washes the disciples' feet at the last supper.
Reception.
Luxenberg's book has been reviewed by
Blois (2003),
Neuwirth (2003)
and following the English translation by King (2009)
 and Saleh (2011).
The most detailed scholarly review is by Daniel King, a Syriacist at the University of Cardiff, who endorses some of Luxenberg's emendations and readings and cites other scholars who have done the same, but concludes: 
The conclusion of King's article summarizes the most prominent reviews of Luxenberg's work that have been published by other scholars.
Gabriel Said Reynolds complains that Luxenberg "consults very few sources" -- only one exegete (Abu Jafar al-Tabari) -- and seldom integrates the work of earlier critical studies into his work; "turns from orthography to phonology and back again"; and that his use of Syriac is "largely based on modern dictionaries".
Robert Hoyland argues against Luxenberg's thesis that Syro-Aramaic language was prevalent in the Hijaz during the time of the Quran's inception, finding arabic script on funerary text, building text inscriptions, graffiti, stone inscriptions of that era in the area. He further argues that Arabic evolved from Nabataean Aramaic script not Syriac. He concludes that Arabic was widely written, was used for sacred expression and literary expression, and was widely spoken in the Middle East by the seventh century CE. He proposes that "the rise of an Arabic script in the sixth century" was likely the work of "Arab tribes allied to Rome" and Christian missionaries working to convert Arab tribes.
The Quran is "the translation of a Syriac text," is how Angelika Neuwirth describes Luxenberg's thesis – "The general thesis underlying his entire book thus is that the Quran is a corpus of translations and paraphrases of original Syriac texts recited in church services as elements of a lectionary." She considers it as "an extremely pretentious hypothesis which is unfortunately relying on rather modest foundations." Neuwirth points out that Luxenberg doesn't consider the previous work in Quran studies, but "limits himself to a very mechanistic, positivist linguistic method without caring for theoretical considerations developed in modern linguistics."
Blois (2003) is particularly scathing, describing the book as "not a work of scholarship but of dilettantism" and concluding that Luxenberg's "grasp of Syriac is limited to knowledge of dictionaries and in his Arabic he makes mistakes that are typical for the Arabs of the Middle East."
Saleh (2011) describes Luxenberg's method as "so idiosyncratic, so inconsistent, that it is simply impossible to keep his line of argument straight." He adds that according to Luxenberg, for the last two hundred years, Western scholars "have totally misread the Qur'ān" and that, ad hominem, no one can understand the Qur'an as "Only he can fret out for us the Syrian skeleton of this text." Summing up his assessment of Luxenberg's method, he states:
Saleh further attests that Luxenberg does not follow his own proposed rules.
Richard Kroes in a review on Livius.org describes him as "unaware of much of the other literature on the subject" and that "quite a few of his theories are doubtful and motivated too much by a Christian apologetic agenda."
Patricia Crone, professor of Islamic history at the Institute for Advanced Study, Princeton, in a 2008 article at opendemocracy.net refers to Luxenberg's work as "open to so many scholarly objections" and "notably amateurism".