5) Appointment with Death - One of Christie's Middle Eastern mysteries, this one set in Petra. This is one of her prime examples of the least likely suspect mysteries, and the victim is one of the most evil people in the Christie canon. I don't think there can be much question about Christie's feelings on evil after this book.
3) The Hollow - This is a story that just sticks with me. The set-up is simple, but effective and the solution even more so. Along the way, we get to know each of the characters in more detail in all of their conflicting thoughts and behavior. I always wonder how much of Christie's own experiences were used in writing about a woman whose husband is unfaithful.
2) And Then There Were None - this book has been on almost everyone's top 5 lists. How can you top a book where everyone is a victim and no one is the killer?
1) Death on the Nile - without a doubt, my favorite Christie. So much so that I actually went to Egypt and took the same cruise up the Nile (though no one was killed on my cruise, more's the pity.) I particularly enjoy the Middle East books by Christie and this is by far the best of them. The book is an incredibly well-plotted mystery along with one of the best cast of characters. Even the minor characters are memorable. There's humor in the book as well as a compelling mystery.
My 6-10 would likely include: Why Didn't They Ask Evans?, Evil Under the Sun, Sleeping Murder, The ABC Murders, and The Murder of Roger Ackroyd.