Crisp and Smart
Legend is told from the perspective of two of the only kids in the Republic who scored perfect 1500s on their Trials, so it makes sense that the writing style would be crisp, intelligent, and never muddled since it's told from their points of view. Day and June are super smart, and the story is consistently told in a thoughtful and intelligent manner. They explain things that have happened in the past in a succinct way, and always take the time to think about what's going on.
Even when Day's mother is killed in front of him, he takes the time to consider what June has been going through:
June was not the one who shot my mother. She was not the one who'd brought the plague into my home. She was a girl who'd lost her brother, and someone had led her to believe I did it, and in anguish she had tracked me down. (2.9.24)
Because the writing style is so clear and intelligent, it makes it so that the reader never gets lost in a story rife with twists and turns. Even if nothing's certain, and the characters seem to be trapped in some pretty dire situations, we still get a good play-by-play that helps us follow the action—and see the emotional sides of the characters and how they relate to each other.