Co-op in Clean The Library works when it makes the library smaller for each player. If every friend runs toward the same loose books, co-op becomes slower than solo because players block paths, move books away from each other, and repeat the same label checks. The best team runs divide work before the room becomes messy.
Start by assigning zones. One player handles one shelf area, another handles a different area, and a third can act as a runner between floors or piles. Zone names can change by server or update, but the principle stays the same: each player owns a set of shelves. If you find a book for another player's zone, drop it near that zone or call it out instead of carrying it through your own route.
Use staging piles as team handoffs. A good pile tells the next player what to place without a long explanation. Place books near the shelf area where they belong, not in random middle paths. Because books save on the floor, staging can be reliable, but only when the pile is readable. If two players keep dropping different shelf zones into the same pile, the pile stops helping.
Give route tools to the player who can use them best. If key-route notes or abilities improve carrying, movement, or sorting, the team gets more value by changing jobs after unlocking them. A faster runner can collect distant books. A player with better carrying can move grouped stacks. A player using shelf-finding help can clean confusing areas while others keep obvious shelves moving. The reward is wasted if everyone continues doing the same slow job.
For timed badges, co-op needs fewer arguments and more repetition. Decide who starts on which floor, who collects route tools, who handles leftover piles, and when players switch zones. A bad switch creates duplicate travel. A good switch happens when one zone is nearly empty and another zone has a clear backlog.
For 8-player or large-server runs, avoid overloading one area. More bodies do not automatically create speed. Use extra players as dedicated runners, second-floor cleaners, staging helpers, and final-check players. The final-check job matters because a nearly complete library can still waste minutes if everyone assumes someone else has the last few books.
If you are playing casually, the same rules still help. Split the library, call out piles, and keep books near the shelves they belong to. Co-op feels smoother when every book moved by one player makes the next player's job easier.