Agatha Christie Slam!

Secret Adversary
This book introduces us to Tommy and Tuppence, two not-quite-cheerfully-broke young folk in the aftermath of the Great War who are looking for any kind of work. They make a pact to place an ad looking for adventure, and are overheard— finding out that adventure is quite easily available, if you're willing to get into trouble. As amatuer sleuths, they are quite entertaining, especially as the rambunctious Tuppence is apt to get in over her head due to her insatiable curiosity.

Partners in Crime
Tommy and Tuppence, now a bit older, are approached to take over a failing detective agency that might lead England's intelligence agencies to foreign agencies in Britain. The chapters could almost function as short stories, little mysteries to be taken in short gulps.

N or M?
With the advent of a new war, Tommy and Tuppence are feeling a bit left out. The nurses don't want Tuppence and the Army doesn't want Tommy. Moreover, their loving children think their parents are a bit barmy for wanting to help and encourage them to allow the young folk to do all the work. As you can imagine, this is somewhat maddening.

Finally, though, Tommy is approached to help flush out a spy in England, or possibly two, ones who might be poised to sneak enemy Germans into the country. And Tuppence can't help getting involved either...

By the Pricking of my Thumbs
While visiting an elderly relative in a nursing home, Tommy and Tuppence stumble on a new mystery to solve. It's a picture of a place that Tuppence has seen, and in tracking down the location, she little knows that the sense of menace she feels will lead her to new intrigue, and great personal danger. You'd think that tracking down one old lady would be a safe occupation...

Posthern of Fate
I read this one first, and was thoroughly unimpressed. Yes, Tommy and Tuppence find a new mystery to solve in their retirement years. But the entire time I was wondering why anybody cared; it was simply a very cold case of murder, and most of the so-called action took place at home. Tepid, certainly, at best.

One final note on Tommy and Tuppence: As many times as they get hit on the head in these novels, it's a wonder they aren't permanently damaged.