Book Recommendation on the four caliphs of islam

Lately, I’ve been deeply fascinated by the life of Hazrat Umar Ibn Khattab (RA)—his leadership, justice, and the way he shaped the early Muslim world. This has made me curious to learn more about the Four Caliphs and how Islam was after our beloved Prophet Muhammad (ﷺ).

Can anyone recommend detailed and well-researched books on this topic? I'm looking for something that covers their governance, challenges, and contributions to Islamic history. Any suggestions would be greatly appreciated!

JazakAllah Khair in advance!