Stephen A. Kent, a professor of sociology who researches new religious movements, described the work as "an unrivalled piece of superb scholarship".

Marco Frenschkowski, writing in the Marburg Journal of Religion in 1999, describes A Piece of Blue Sky as "the most thorough general history of Hubbard and Scientology, very bitter, but always well-researched.

[4] The Tampa Tribune-Times said that Atack's provision of extensive detail and source notes for each claim sometimes gets in the way of the story, but prevents the book from being just another bitter diatribe against Scientology.

Jon Atack (born Jonathan Caven-Atack in 1955) is a British author and artist who is widely recognized as one of the most informed critics of the Church of Scientology.

He also objected to being told not to have relationships with so-called "suppressive persons", meaning those whom the Scientology organisation had declared enemies with whom members should not communicate.

[10] The court ruled that the manuscript might discourage people from buying Hubbard's books by convincing them he was a swindler, and that copyright law protects rather than forbids this kind of criticism.