Okay, so there seem to be a lot of lists around picking the best of the Christie novels on the occassion of her 125th birthday.
I had to join in. I've been reading Dame Agatha since I was a teenager, and my father brought home a copy of The Underdog and Other Stories, saying "I think you might like this." Truer words were never spoken.
I've read all of them and at various times, I've reread them as well. I've collected them for nearly 40 years, and currently have American 1st editions of all of the novels and short story collections. It took me a long time to do it, but the collection is looking great. I'm going back at this point and adding copies with dust jackets when I can afford it, but they're all there.
1) Death on the Nile -- I enjoyed this book so much that I actually took the same cruise as Poirot and company. I'm glad I did that before 30, since I don't know that I'd go back in the current climate, but it was an adventure. The book is fascinating, and perhaps her best Poirot novel.
2-5) The Big Four -- no not that book, but the four that made her reputation. The Murder of Roger Ackroyd, And Then There Were None, Murder on the Orient Express and Curtain. For their own reasons, they were daring and showed Christie's versatility as an author.
6) A Murder Is Announced -- the best of the Miss Marples by far. A stunning plot, and an intimate look at post WWII life in a village. For all of those who say Christie is only plot, I always point them to this book. Plus the murder of a LGBT character was probably the most heartbreaking scene I've ever read in a Christie.
7) The Hollow -- another Poirot that stays with me. The portrait of Henrietta as artist and human is probably quite like what Christie felt about herself -- cannibalizing everything.
8) The ABC Murders -- another first, one of the first serial murder books and one that is still mentioned today. I've read other titles that refer to the ABC Murder type.
9) Why Didn't They Ask Evans? -- they didn't mean Curtis. I love what Christie does with plot here. The care with which she must have planned this book to achieve what she did here makes me stand back and gawk. Plus I've always adored her Bright Young Things, and Lady Frankie and Bobby are among the best.
10) The Underdog and Other Stories -- tucked in my collection of first editions is the book that my dad gave me 40 years ago. I may be a bit sentimental about this title, but it opened the world of mystery to me and that is worth a spot on my list.