I know that this book can be obtainable during the Roshamuul task Soothing Bad Dreams (the one that you need to do 20x to open the Dark Grounds - big robots area), but I've already done this task +40x and every time I said "lost" to the npc to be able to try to get another book.
Is it sheer luck? Or do I need to do something different? (maybe trying another plant).