This has to be one of Agatha Christie's best ever books. There are a lot of them, yes (Around 15!) but i would suggest that this taut thriller is probably within the top five.
The characters are very well drawn. Realistic and believeable. The story is tense, not too overdramatic, and suspenseful. The story begins brilliantly (rather like the beginning of And Then there Were None) with all the characters seperately going about their own thing, slowly unfolding the reasons why they come to be at Gull's Point over this fateful weekend. It opens with esteemed lawyers discussing criminal trials...then moves to a murder carefully planning out the deed...onto newlywedded famous tennis player with his new wife Kay...to the attempted suicide of man by driving himself over a cliff. (A man to return to Gull's Point in the future to see the place where he almost died, only to become an important factor in a murder investigation that will change his life...and so on.
The setting is good. The plot is different from some of her other stuff. (Something all her best books have in common, an element of extreme originality in solution, plot, setting, or character.)
This is actually a brilliant thriller. The atmosphere is fear-filled, and the solution brilliant. She double-trumps the reader's expectations and assumptions once again, in an incredibly fine detective novel.