This was the first book by Agatha Christie that I read and I guess I picked up a wierd one. It is based in 4000 year old Egypt. It is not about some secret tomb or pyramids, but does describe the different belief system (related to death) in Egypt. 
 One good thing holding this book together (among some others too) is its plot. Things turn bad at a quick pace and the story remains unpredictable even upto the end. I kept on guessing the murderer (/s), but remained unsuccessful until the author herself told it. Good as a one time read.