I am sure it was the reader's 'fault' in that they failed to search properly for their desired book, but I recall reading a couple of nasty reader reviews where the readers slated the book they'd bought because it was not the one they had wanted to buy.
Of course, they were after the bestseller, and what they got was something they perceived as markedly lesser. Oh dear!
Some will then take to the reviews section and sound off without even contemplating how it was their own fault by just searching against title and clicking 'buy now'.
I once also read a review where the reader had clearly bought the wrong book, read it, and then criticised it because it did not follow the plot that other reviewers had mentioned, ha. They never even realised they'd bought a different one and seemed genuinely perplexed.
So, I don't think you should name your book the same as someone else's, especially if the other one is a top-seller... but having said that, it could mean you gain some sales to which you were not entitled! :D That could backfire or could work in your favour. It'd be an interesting ride... On a legal front, I can't see that it can get you into trouble, though, unless your book somehow emulates the other to try and pick off sales.
Annie