"William Atheling" is a pseudonym of James Blish.
He adopted it in order to write reviews of SF magazines in a fanzine. The reviews are technical in nature and brutal. They are also a useful lesson for beginner writers in What Not To Do. The harsh style is hilarious and it is notable that those who come in for the most severe criticism are not familiar names to the SF readers who came to the genre after the era of the pulp magazines. Readers of the column actually complained when Blish praised some material instead of simply dipping his pen in the vitriol bottle every time, but this further illustrates that no matter how acerbic the criticisms are, they are not indiscriminate.
The book is as easily read as any of Blish's fiction and as entertaining.