Agatha Christie 
The Mysterious Affair at Styles (Annotated) 

The Mysterious Affair at Styles is a classic detective novel by Agatha Christie and features her iconic detective, Hercule Poirot. The story is set in England during World War I and revolves around the wealthy widow Emily Inglethorp, who dies under suspicious circumstances.

Captain Arthur Hastings, a friend of the family, enlists the help of Hercule Poirot to investigate the case. As Poirot delves into the intricate web of relationships and motives among the residents of Styles Court, he uncovers hidden secrets and deceptions. The novel is filled with red herrings, twists, and clever detective work as Poirot uses his 'little grey cells’ to solve the mystery.

The book not only introduces readers to the brilliant and eccentric detective Poirot but also showcases Agatha Christie’s mastery of the mystery genre. It’s a compelling whodunit that keeps readers guessing until the very end.