Crocodile on the Sandbank - Elizabeth Peters
I disliked the ending so much when I first read it, that I didn't want to try the next in the series. Years later, after reading another book set in Egypt which I loved ( by Barbara erskine ), I dug out the Elizabeth peters book again, and realised how brilliant it was. I still didn't like the ending, but tried the second in the series and then realised why the author had had to give that particular ending. I know it's all a bit cryptic, but saying what the problem was, would spoil the book for others.