Here are a few scholarly reactions to the book:
Dr. William Lane Craig
“Aslan has offered nothing new under the sun when it comes to offering a critique of the historical Jesus,” Craig said in a recent press release distributed in an effort to decry the book. “In fact, he is attempting to revert scholarship back to the early 1900’s by echoing Albert Schweitzer’s book, ‘The Quest for the Historical Jesus.’ Like Schweitzer, Aslan claims that Jesus is historically unknowable and we can never get back to the real Jesus.” 
Dr. Craig Evans
"Zealot is riddled with errors, probable errors, and exaggerations. Aslan tells us a builder in Nazareth had "little to do." Excavations at Nazareth and nearby Sepphoris suggest otherwise. Being a builder (or "carpenter") meant that "Jesus would have belonged to the lowest class of peasants in first-century Palestine." Where does this come from? Sepphoris, a major city of Galilee, is said to be "a day's walk" from Nazareth. Actually, it takes a jogger about 45 minutes. Scholars will be surprised to learn that the first-century Jewish prophet Jesus ben Ananias, mentioned by the historian Josephus, prophesied the 'imminent return of the messiah.' He did no such thing." 
See Evans's entire review here.
Dr. Gary Manning, Jr.
"Aslan repeatedly presents highly unlikely interpretations of passages in the New Testament, makes little effort to defend those interpretations, then moves on as if he has made his case. Suffice to say this, as others have said before: there is something a little bizarre about using our only historical documents about Jesus (the New Testament) to come to conclusions quite in opposition to those documents. There is a good reason to believe that Jesus claimed to be a divine king and savior who would die and rise again, and would one day return to judge the world: All four gospels, and indeed the entire New Testament make this claim. You can deny that this claim is true, but it is scholarly folly to deny that Jesus and the early Christians believed it." 
See Manning's entire review here.
Zealot: The Life and Times of Jesus of Nazareth by Craig Blomberg
Courage and Godspeed,