Four fans will be thrilled to read more (and overlapping!) stories from a favorite character's perspective. Especially since, even in the stories before he meets Tris, readers learn more about his background, his early Dauntless friends, and his state of mind in the two critical years before Tris joins him in the Faction and changes his life. Not much of the plot details or characterizations will be revelations to Divergent readers, but Four's voice is actually sharper here than in Allegiant, where it was sometimes easy to confuse with Tris' POV.
Ultimately, these stories are like the special features on a DVD: fun to experience but slightly unnecessary to the overall appreciation of the work (in this case, the Divergent trilogy). Four's appeal is partially due to his quiet strength, his mysterious background, and his ability to show his vulnerable side to Tris. Roth added his point of view in Allegiant, so there's nothing particularly novel about his voice in these stories. Still, it's fun to revisit secondary characters (Uriah's older brother Zeke, Shauna, and Tori are especially well represented), even if you know what will happen to them. And, of course, it's especially lovely to see some moments from Divergent retold from Four's point of view, because it shows how Tris didn't always know what he was thinking or feeling about her.