What book was it? I wish to read it.
Christianity and Liberalism by J. Gresham Machen.
Machen was one fo the ministers of the 20's (along with Louis Sperry Chafer, and Carl McIntire) who stood up to the liberals who were replacing Christianity with another Religion.
Machen's book exposed their methods.
The hyperlink above will link you to the text of the book. You can probably copy/paste to your favorite word processor/editor, and read it at your leisure. i don't think that there would be any copyright problems.