I’m interested in learning more about the history of the far-left and what the different "factions" (Leninist, Maoists, etc) believe in and how they're different from each other. This is probably a pretty broad topic and there's probably not one book that covers everything, but any books on any of the belief systems would be helpful. I’m guessing that the Communist Manifesto is a good starting point? I’m also looking for other books like the Communist Manifesto about these other “factions”. Thanks in advance!
The Communist Manifesto is not really a good starting point. By all means read it, it's quite short and much more readable than Capital, but it won't tell you much about about how Communism developed politically, much as reading the Bible won't tell you much about the difference between Christian sects.
As a general survey text, I'd recommend Archie Brown's The Rise and Fall of Communism. David Priestland's The Red Flag is less analytically sharp but it serves as a useful reference to global communist movements and goes into a bit more depth about Asia.