Here is the full list of all 9 Detective Grimoire achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Complete the game
Complete the game 100%
Full suspicion on the culprit, none on anyone else
Get inside the tent
Read the letters on Remington's desk
Draw a cute ghost in your notebook
Finish speaking to the Little Girl
Examine all the Boggy merchandise
Examine the crime scene