A somewhat surprisingly contained story with talented art to support it. I felt that a side story or two possibly had more value than the main story but that doesn't mean the story wasn't gratifying. However, if you are pressed for time or you are indifferent to Levi but want slightly more Shingeki no Kyojin, I could recommend you to wiki the story and instead read the final interaction between Levi and Erwin. That may seem snide but I genuinely believe that it is applicable to many or most Shingeki no Kyojin fans.

Basically, this is a complementary manga to the world of Shingeki no Kyojin but offers too little information on Levi's origins and lacks exposition and commentary to such a unique world. The supporting characters are only there for that exact purpose; to carry the story forward. Interactions involving the supporting cast are basic and only towards the very end, in my opinion, do they contribute anything of value to the narrative which happens to reinforce Levi's resolve.

Commendation has to be credited to the author and artist for creating a successful spin-off which surely was a difficult task. Without my research, Hajime Isayama's editor must've done his best to capture and communicate his mangaka's vision to the author's of this spin-off. Despite the barrier of making something inside another's fictional property. Hikaru Suruga's art was highly consistent and has great talent but suffers ultimately just from the fact that he isn't Isayama. Perhaps this applies to other areas too but there is no point discussing what could've been better had Isayama made this.