According to this book, James Comey's alignment is Lawful Good (I'd go so far as to call him a paladin), and Trump's is chaotic evil. No wonder they didn't get along.
In the first chapters, Comey describes his formative years and early career, focusing on leaders who made an impression on him, including his boss at his first job. He then moves on to the reasons you bought this book: the reasons why he made his much-discussed announcement about reopening the investigation into Hillary Clinton's email; his private meetings with Donald Trump, and his eventual firing.
All in all, he comes across as honest, and with a deep love and appreciation for the institutions that make America free. As far as I can tell, the book lines up with what we the public know from news reports. I could be wrong, because who can keep up anymore?
If you're a Trump supporter, you won't like the comparisons Comey draws between Trump and the Mafia bosses he used to pursue earlier in his career. But even so, the book is worth considering for its insight into what makes a good leader, and why separation of powers makes America strong.