Disclaimer: I'm a bit of a Carr fanboy, so I tend to rate his novels over Christie's, but I still like Christie's novels.
To wake the dead
Not one of Carr's more famous novels, but I got a soft spot for this one. The final confrontation with the murderer is one of Carr's most dramatic ones, and it works very well with the mood. The mystery won't blow you away, but I love the tone Carr uses here.
The blind barber
This novel features more humor than most of Carr's novels, plus he makes fun of Hitler. So there's that.
The crooked hinge
I'm just gonna say this: the solution is literally longer than the problem itself. Depending on how you reacted to that point, you might love or hate this novel. I personally love it.
The case of the constant suicides
I freaking love this novel. It's by far the best Carr novel out of those 4, and is the most inventive of them all. Would recommend this one.
Christie time:
The ABC murders
This book is evidence that when Christie was at her best, she really was one of the best. Love it, recommend it too.
Thirteen at dinner
This is a very Christie book. This is to say it's not bad, but it's one of her novels that just don't blow you away.
Cards on the table
If you like "Dream Teams" you'll be happy to know that both Poirot and Battle(from other Christie novels) work together to solve this case. The murder itself is pretty fun, but the most fun part is that Poirot and Battle are working together.
Death on the Nile
One of Christie's most underrated(though not by much) most brilliant novels. Pretty fair, you should be able to solve it without difficulty. Still, pretty inventive for its time and makes use of many techniques that make its resolution very satisfying.
Crooked house
Ahhh this one is...interesting. It's a slightly(very slightly) meta detective novel in that you'll enjoy it more if you have read more mysteries before it. Still great novel otherwise, even if the culprit's motive, however amazing, might make you go "What."
Ordeal by innocence
The seven dials mystery
Gonna put it this way: I didn't like this novel, too melodramatic for my taste.
Murder at the vicarage
Love it, one of my first Marple novels and one of the best in my opinion. It...does stretch credibility at one point though.
Dead mans folly
Sad cypress
Towards zero
N or M?
This is one of Christie's thrillers featuring Tommy & Tuppence. First things first: Those thrillers should be read in order to fully appreciate the character development. So don't read this without reading Secret Adversary/Partners in Crime first. Note: Christie's thrillers somewhat read like "Thrillers for people who like murder mysteries" which is great for me, but it doesn't work for everybody.
I'll comment on the other novels later if you want, I kinda gotta go now.