I am interested in the history of the early 20th century, but realized that I had little to no knowledge of how the concepts that constitute liberal democracy formed before the 20th century. Are there any extensive studies about how it developed?
Whilst I wouldn't call it a study, I'd still say that Age of Revolution by Hobsbawm makes for a very accessible introduction to the emergence of liberal democracies.
He outlines the social and economic situations that existed then shows how the dual French and Industrial revolutions changed both the economy and culture of Europe. For example, the rise of modernism in philosophy and governance was fundamentally linked to the idea that classes could advance. It's quite old but a very good introduction