I think this is a wonderful murder mystery that is perfect for all readers. It is one of Agatha Christie's first books, and it introduces one of the greatest fictional detectives of all time: Hercule Poirot, an impressive character. It also showcases some very outstanding vocabulary, and I was extremely impressed.
It is set during the First World War in Essex, a little town of the countryside in England. The story is told from the point of view of Mr. Hastings, a simple man who is friends with John Cavendish, whose aging mother owns a cute little manor called Styles Court. John's mother, Emily Inglethorp, has just recently been remarried to a strange fellow with a long black beard and glasses, Mr. Inglethorp.
Mr. Hastings arrives to Essex from a train and meets his friend, John, and then they go to the estate. They have plenty of company there, including John's wife (Mrs. Cavendish), Lawrence Cavendish, the younger brother of John, Dr. Bauerstein, a medical professional, and a few others.

The day after his friend arrives, John Cavendish's mother is murdered. It is supposedly strychnine, one of the deadliest poisons. They try to figure out who the culprit is, but their attempt is weak. Mr. Hastings hears that his old friend, Hercule Poirot, is in town, and gets a hold of him, and helps along in the revealing of the case. Poirot is an outstanding fellow. He has ideas that, at first, seem ludicrous, but then they turn out to be very orderly and sensible.

My favorite part of the story was when Poirot, aided by Mr. Hastings, announces the final culprit. I won't tell you who it is, but I will tell you this: It is said about Agatha Christie's books, that none, or very few, readers can find out the person that committed the crime until they get to the end of the book.
This mastermind, Poirot, takes the reader through the twists and turns of the mystery, and the ingenious writing of Agatha Christie adds flair to the exciting plot.
I recommend this book to everyone 11 years old and up, because there aren't any bad situations or vulgarities, but the vocabulary is a bit challenging. This book is truly amazing. I recommend that if you don't read this book, at least read one of her others.