I'm always a bit suspicious when people point to 'The Gay Science' as some kind of blueprint for modern thought. Don't get me wrong, Nietzsche is foundational, but the way his ideas get filtered through modern 'self-help' or pop-philosophy really grinds my gears. His concept of creating your own values after declaring 'God is dead' is the big one, but modern existentialism and postmodernism took that ball and ran with it, sometimes in directions he'd probably hate. The emphasis on art, creativity, and life as an aesthetic phenomenon—that's all over 'The Gay Science'—feels incredibly relevant when you look at how contemporary philosophy grapples with meaning in a secular world. It's less about systematic arguments and more about aphorisms, style, and perspective, which itself influenced later thinkers who rejected grand, sterile theories.
My undergrad professor used to say you can draw a straight line from Nietzsche's playful, probing style in this book to the whole deconstructionist movement. The idea that truth isn't just discovered but constructed, that our perspectives are fundamentally limited—it starts right there. It's funny, I first picked it up expecting a dry treatise and found a surprisingly vibrant, almost poetic text that made me question why philosophy had to be so boringly serious all the time. That shift in tone alone was an influence.