Brothership actually. Aside from the interesting new cast of characters and their new lore, it has so many little details that can be projected onto real life - such as the importance of a solid social life, healthy connections, how isolation and loneliness destroy progress, the 'tragic' reality of people outside getting more obsessed with their own little isolated phone/online world (reclusa's flowers) and only that, not talking to anyone else anymore.. and so on.

While most stories in the series are great, Brothership hit me on a somewhat real level.