Looking for book recommendations on republics, royalism, and constitutional monarchy

Hi everyone.

I’m an Iranian who currently leans secular republican, but to be honest, most of my own beliefs were shaped by the same things that influence a lot of people around me: whatever my dad debated with taxi drivers, random conversations, and whatever I saw on Instagram. Many of my fellow Iranians are now supporting royalism or constitutional monarchy, but their understanding also mostly comes from social media and news influencers.

I don’t want to rely on that anymore. I want to actually educate myself with real political theory and understand these systems properly so I can form a fair, informed opinion. I’m genuinely open to changing my mind if the evidence and arguments make sense.

So I’m looking for well-regarded books on:

1. the political philosophy behind republics and democratic systems

2. the theory and practice of monarchy

how constitutional monarchies function in the real world today

1. comparative political systems

historical and cultural factors that make people support one system over another

If you know any books that are commonly recommended in political science or history courses, or even good introductory reads that explain these ideas clearly, I’d really appreciate it.

Thanks in advance for any credible recommendations.