In *Kingdom Come: Deliverance 2*, a crucial side quest, easily missed and unrepeatable, involves retrieving Rosa's book. This guide will show you exactly where to find it.
Unlocking Rosa's Book Side Quest
Before Rosa requests the book, complete the "Via Argentum" quest and begin "Taking French Leave." After assisting the Ruthard family with Vavak (through force or diplomacy), speak with Rosa to learn about a secret Maleshov passage for rescuing Hans. She'll mention the book, and asking about it will initiate "Rosa's Book." This quest is only available during "Taking French Leave." Failing to find the book before leaving with Hans permanently locks you out of completing it and potentially progressing a romance with Rosa.

Locating Rosa's Book in Maleshov
Upon entering Maleshov, Hans is in the largest tower's top floor. Use the external stairs to enter. Inside, more stairs lead to a small kitchen. Wait for the guards above to leave before proceeding.

Stealthily ascend the stairs. A room contains Lady Ofka. Knock her out, and take the keys from her, the podium, and the chest (which also contains a sword). Rosa's book is in a red volume in the window alcove to the right of the fireplace. Grab it, and your objective updates to returning it to Rosa.

While there, take the sword from the chest in the adjacent room; this saves time later when equipping Hans and his guest. Proceed to the top floor, unlock the left door, and trigger a cutscene.
Completing the Quest
After the cutscene, continue "Taking French Leave." Guide Hans to the stables, dealing with guards along the way. Once at the stables, another cutscene plays, concluding the quest. Return to Kuttenberg City and deliver Rosa's book to Ruthard Palace.