Constraints and Resolution
I really liked this book. This story is a thrill ride. Ten people in clear view of their own death coming and (nearly) helpless in the face of it. A masterful work of story telling and suspense.

An analysis of Agatha Christie's "And Then There Were None"
Let me say from the outset that I really liked this book. This story is a thrill ride. Ten people in clear view of their own death coming and (nearly) helpless in the face of it. A masterful work of story telling and suspense. I was at the edge of my roller coaster seat, feeling the wind go by, heart pounding. Christie has been spot on with the depiction of an atmosphere of tension and the psychological ramifications of staring death in the face: the tricks of the mind, the distrust, the impact of environmental conditions on the mood, and so on. The grey areas of guilt and murder just beyond the law is a great concept to work and it is truly difficult to side either with or against the perpetrators in regard to the various situations presented. For mystery buffs, this is a no-brainer recommendation - it has to be one of the best mysteries out there. Even non-fans of the mystery genre (myself included) will surely enjoy it. If you haven't read it, I highly recommend reading it before you read any further.
The real reason I am writing this review is a more detailed analysis of the plot and its resolution. There is no doubt in my mind as to the effectiveness of the setting of the plot, the reactions of the people and the tension. The resolution is (for the most part) satisfying, though not completely infallible, and this is the main point of my analysis. All opinions are, of course, subjective and my own.
Full spoilers ahead
There is an inherent amount of constraint in the ways the murderer can go about his task, and by inherent I also mean significant - so much so that seemingly impossible constraints somehow seem to work themselves out in favor of the murderer. The biggest constraint of all (as I see it) is the adherence to the nursery rhyme at all stages. Next would be the order of victims, which is suggested to be mostly in decreasing amounts of guilt. The task is already a difficult one, but its execution with conformity to the rhyme simply cannot be completely planned in advance, and it just worked out that way because the author wanted it to. I will demonstrate my point with examples.
Eight little soldier boys traveling in Devon;
One said he’d stay there and then there were Seven.
This is in reference to General Macarthur who "realized that he didn't want to leave Soldier island" because he decided to face his judgement with open arms. However, this is not known to Wargrave since it is an insight offered to the reader as Macarthur is going to sleep at the end of the first day after two murders. How did Wargrave know that the General is the next victim, or that he will sit meditating on the edge of the cliff, waiting for his doom? The epilogue mentions that Wargrave has meticulously thought out details such as the order of the victims, surely he placed the General third during his planning? But he could not have predicted his behavior to give him an opportunity so in line with his planning and the verse of the rhyme. This is the problem with multiple constraints like this. The alternative would be that Wargrave has not decided the exact order of the victims, but simply has a general rule. That would mean he is leaving a lot to chance and opportunity at the time of execution. For this particular instance though, I guess I can grudgingly give the benefit of doubt to Wargrave (and to Christie) - may be he knew more about Macarthur than is mentioned (some private conversation on Day 1), and he anticipated this behavior.
The part from where stuff really starts getting unpredictable and a bit ridiculous is after Wargrave fakes his own death. I can buy that Armstrong is gullible enough to go alone with Wargrave at two in the night near the edge of the cliff. It is the three murders after this that I really have a problem with.
Three little soldier boys walking in the Zoo;
A big bear hugged one and then there were Two.
We are left with Vera, Lombard and Blore outside the house in the sun debating on going back in to have lunch inside. Vera is adamantly against this, Blore wants to go in. Lombard decides that he will stay with Vera after she mentions that she anyway couldn't eat the same tinned tongue again. My point is, Lombard isn't particularly leaning one way or another, it just so happened that he decided to stay with Vera. If Vera hadn't been so adamant in the first place, most likely all three would have gone back in for lunch. As it so happens, Blore is the only one who decides to go in and is killed by a falling block of marble just outside the house, courtesy Wargrave. There is so much that worked out by chance here. How could Wargrave have counted on one of them being separated? In fact, how could he even have known that they would exit the house in the morning? Maybe one of them falls sick after the events of the last night (it isn't very unlikely considering the tension) and all of them decide to stay in. What would have happened if one of more of them had accompanied Blore? Would Wargrave have risked giving away his position? Or tried to kill them all with the marble block? But that wouldn't be in accordance with the rhyme would it? Or would he simply have bided his time, hoping for someone - alone - to go back into the house right under the window. Too many constraints which conveniently satisfied themselves.
Two little soldier boys sitting in the sun;
One got frizzled up and then there was One.
One little soldier boy left all alone;
He went and hanged himself and then there were None.
Armstrong's body turns up near the island shore somewhere and Lombard and Vera drag it out of the water. Vera picks the revolver from Lombard's pocket while they are involved in this and ultimately ends up killing him in some kind of self defence. A lot hinges on Vera being the one to truimph in this situation. In the epilogue, Wargrave mentions that Vera was "a daring and resourceful young woman. I always thought she was a match for him and more". That she may be, but I really doubt that she is a match for Lombard with a revolver. For all his cunning over years of tough spots, Lombard really doesn't see the trick Vera pulls with him? I understand that his cockiness and overconfidence has time and again been highlighted, but it is still a stretch of imagination to assume that Vera, with her psychological troubles, can get the better of him. Again, Wargrave could never have known that Vera would prevail in this last standoff. It is just faith and luck at this point. And it is crucial that Vera succeeds because it is just not possible that Lombard hangs himself. Also, once Armstrong is seen to be dead, both should immediately know that a third party is at play here. Both were together (each can vouch for the other) when Blore was killed. Even if Vera kills off Lombard, it is not justified for her to let down her guard and go into the house feeling all relieved even though I can buy the fact that she could commit suicide under a sufficiently hypnotically suggestive environment.
These final murders are the hardest for me to get on board with and it is here that Christie seems to bend a few rules here and there to get her murderer to succeed through all constraints. I probably wouldn't go as far as to call it a deus ex machina, but it lies in a similar ballpark.