Sherlock Holmes Chapter One

This achievement is missable, and is earned in the side-case 'The Missing Shopkeeper'. You can accept it from the desk lady in the Cordona Chronicle (you must hand in the prior side case 'Eel Hunting' first, you cannot stack cases from the same questgiver).

Towards the end of the case, you follow some tracks to a hideout, with a sort of dungeon area. After liberating it and finding all evidence in this hideout (namely the crime scene), you will find a key. Access the cell with a bloodied bed, and you can retrieve the book. If you can't access it, you need to search around for more clues. Hand in the quest back to the quest giver and you'll unlock the achievement.

If you're struggling, this is a great walkthrough (credit to 'AfterGames')