Looking somewhat later, I find it interesting that "bookcase" and "bookshelf" become prevalent in Google's Ngram Viewer only comparatively late in the 20th century. "Bookcase" starts its ascent around 1900 and peaks in the 1930s, "bookshelf" really doesn't become particularly prevalent until after 1980.

<https://books.google.com/ngrams/graph?content=bookcase%2C%20...>

This corresponds roughly with cheap mass-market books becoming widespread, particularly paperbacks (mid-1930s, large growth in the 1950s).