Nothing about Kanan was set up to succeed. It is a tie-in to a children's animated series, starring a character most comics readers had met once, published in the shadow of two ongoings with far bigger names attached. It is also, twelve issues later, one of the two or three best things Marvel did with the licence in the 2010s.
Order 66 from the inside
The advantage Greg Weisman has is proximity: he was executive producer and story editor on the first season of Star Wars Rebels, the series that introduced Kanan Jarrus, so the book is not an outsider's interpretation. The first arc opens with the massacre and then keeps going past the point most Star Wars stories stop — into the years of a teenager with a stolen name, a hidden lightsaber and no idea whether anyone else survived. Weisman refuses the easy version in which trauma makes Caleb noble. It makes him a liar, a drinker and a very good one.
The framing device does real work too. Each arc is a memory triggered by something happening to the adult Kanan in the Rebels present, so the reader is always watching two versions of the same man decide what to do. When the second arc goes back further, to explain how a Padawan came to command soldiers who would later kill his master, the structure turns the Clone Wars from wallpaper into the reason for everything.
Larraz
Pepe Larraz draws most of it, and the storytelling is exceptionally clean — action that reads left to right without a caption having to explain it, and a real gift for the small acting beat in a wide shot. He also solves the animation-adaptation problem that sinks most cartoon tie-ins: the characters look like themselves without looking like screen grabs.
Where it is limited
It is a companion piece, and it knows it. Readers who have not watched Rebels will follow the plot perfectly and still miss why the last page matters. And the twelve-issue length is a cancellation, not a design: the second arc closes cleanly, but the book plainly had more of this to do.
Verdict
If you have ever wanted a Star Wars comic that treats the Jedi purge as a thing that happened to a specific frightened child rather than as backstory, this is the one. Read it before you read the flagship.