Best Agatha Christie Mysteries to Read

I've tried reading Agatha Christie mysteries over the years and with the exception of Ten Little Indians, I didn't like the books very much. That has now changed. Someone donated a pile of Christie paperbacks to the library a couple of months ago and I took them home to read them to see if they should be added to the collection or at least to our paperback exchange shelf. Whoever you are out there that left these biblio-babies in a basket on the library doorstep, thank you. I now have a new addiction. I plod through the books I have to read for book groups or feel I ought to read, spurred on by the thought that another Christie mystery will be my reward when I finish.
This is the list of what I've read so far with very brief annotations. I recommend all these titles. I have a hunch that Christie's later works may often tend to be too wordy and precious, so don't start with those. Start with books written in the 1920's through early 1950's. I also think I might prefer Miss Marple to Hercule Poirot, but I haven't read enough to be sure and that is purely a subjective comment. Christie's books that have neither of her famous detectives can be quite engrossing too, so give those a try.
My List so far...
Sad Cypress, (1940) a woman on trial for the murder of her rival, Poirot investigates. Christie does trials well.
Destination Unknown, (1954) a cold-war spy story set in Casablanca and North Africa, sort of James Bondish in having a secret location for top scientists who have disappeared and are being tracked by British Intelligence.
The Hollow, (1946) Poirot and the staged murder of a doctor. Classic country house murder.
Third Girl, (1966) set in the 1960's, Poirot and flaky friend/amateur detective, Mrs. Oliver solve a murder. This book was close to being too wordy and meandering for me; Mrs. Oliver particularly is a bit too fluff-headed for my tastes, but try it anyway.
Crooked House, (1949) Greek millionaire is murdered in the sprawling family home.
The Sittaford Mystery, (1931) a seance in a remote house on the moors predicts a murder.Really nice, spooky atmosphere provided by Dartmoor landscape.
The Mystery of the Blue Train, (1928) Poirot solves a murder on a French train to Nice. Stolen rubies make this a classic jewel caper.
What Mrs. McGillicuddy Saw, (1957) Miss Marple's friend sees a murder on a passing train. No one believes her until Miss Marple comes to the rescue.

Agatha Christie, a reader's companion by Vanessa Wagstaff and Stephen Poole is the BHPL book about Christie's works that I consulted to review the plots.