Answer:

Introduction:
The author of the passage comes to know that the English author referred to is Stephen Spender through a book called "The God That Failed". The book is a collection of essays written by six prominent authors, including Stephen Spender, who wrote about their disillusionment with communism.

Explanation:
The passage mentions that the English author was a communist and an atheist. To identify this author, the author of the passage refers to a book titled "The God That Failed." This book was published in 1949 and contains essays by six prominent authors, including Stephen Spender. The book explores the disillusionment of these authors with communism and their subsequent rejection of it.

Significance of 'The God That Failed':
The book "The God That Failed" serves as a key reference to understand the identity of the English author mentioned in the passage. It is a collection of personal essays written by authors who were initially sympathetic to communism but eventually renounced their beliefs. The book made a significant impact at the time of its publication and became a popular reference for understanding the disillusionment many intellectuals experienced with communism.

Relevance of Stephen Spender:
Stephen Spender, a prominent English poet and intellectual, contributed an essay to the book "The God That Failed." His essay, titled "The God That Failed," describes his own disillusionment with communism. Hence, by referring to this book, the author of the passage identifies Stephen Spender as the English author in question.

Conclusion:
In conclusion, the author comes to know that the English author referred to in the passage is Stephen Spender through the book "The God That Failed." This book contains essays by six authors, including Spender, who wrote about their disillusionment with communism. By referencing this book, the author identifies Stephen Spender as the English author mentioned.