Debussy wanted to distance himself from what he considered the emotional excess of the Romantics and instead wanted to write music that, through sound, created an ambience similar to that of the Impressionist painters and Symbolist poets of his day.
All books initially copyrighted in the US from 1964 through 1977 have had their copyrights automatically renewed (by law) and the copyrights are still in force. The initial copyright term was 28 years; the renewal was for 67 more years.
Open your book, and look at the copyright page on the back of the title page. Modern books' title pages tell you what year the book was published and in which edition. Some include information such as the publisher and city where the book was published. Books published from 1970 on include an International Standard Book Number, ISBN.