In *Kingdom Come: Deliverance 2*, missing certain side tasks can lead to their failure, as you won't be able to return to them. One such task is Rosa's book side quest, which is crucial not only for completing the mission but also for potentially advancing your relationship with Rosa. Here's how to find Rosa's book and complete the quest successfully.
To initiate the quest for Rosa's book, you must first complete the "Via Argentum" quest and begin "Taking French Leave." During "Taking French Leave," assist the Ruthard family in dealing with Vavak, using either force or persuasion. After resolving the situation, you'll be directed to speak with Rosa. She'll reveal a secret passage into Maleshov, which you can use to rescue Hans. In the conversation, Rosa will ask you to retrieve a specific book for her while you're in Maleshov. Agree to her request, and the "Rosa's Book" side quest will officially start.
Screenshot by The Escapist
It's essential to complete this side quest during "Taking French Leave," as leaving with Hans without the book will cause the quest to fail, and you'll miss the opportunity to romance Rosa. Fortunately, Rosa's book is conveniently located on your path to Hans' room.
Upon entering Maleshov, head to the largest tower where Hans is held at the top. Use the side stairs to enter the building stealthily. Once inside, you'll find another set of stairs near a small kitchen. Hide in the kitchen until the guards upstairs leave the tower.
Screenshot by The Escapist
Sneak up the stairs to find a room with Lady Ofka, who is facing the fireplace. Approach her from behind and knock her out. Collect the keys from her body, the podium, and a sword from the chest in her room. In this same room, locate Rosa's book to the right of the fireplace in a window alcove. Pick up the red book to update your quest objective to return it to Rosa.
Screenshot by The Escapist
While in the vicinity, grab another sword from the chest in the adjacent room. This will save time later when you need two weapons for Hans and his surprise guest. Proceed to the top level, unlock the left door, and trigger a cutscene.
Following the cutscene, continue with "Taking French Leave." Although Hans refuses to use the passageway, you can work towards romancing him by selecting the heart dialogue option, provided you chose the same in Trosky. Sneak to the north side stables, knocking out and hiding guards as needed. Clear a path, signal Hans, and ensure he reaches the stables safely.
After opening the gate and completing the subsequent cutscene, head back to Kuttenberg City. Make a stop at Ruthard Palace to deliver Rosa's book, successfully concluding the side quest in *Kingdom Come: Deliverance 2*.