This is a story-related achievement, and I don't believe this can be missed. If you die, by selecting "Run" instead of "Fight Back", you may want to quit and reload your file, just in case a retry voids the achievement (it voided "It Came from Beneath the Sink!" for me).
Once you gain entry to the bookstore (see "Are You Terrified Yet?" for more info)
• Select dummy on left, then Slappy will appear shortly after
• Select dialogue "Give Name"
• Select dialogue "Finish His Thought"
• Select dialogue "Bluff"
• Select dialogue "Really"
• Select dialogue "Pry"
(At this point, Slappy's Nightmare unlocks)
• Select dialogue "Scrutinize"
• Select dialogue "Shrug"
• Select dialogue "Made Ya Look"
• Select dialogue "Fight Back"
Some dialogue will follow your selection of "Fight Back", then the achievement is yours once Slappy is back in the book.
If you vote down, please leave a comment and I will edit the solution accordingly.