I've been reading all the old le Carre books. There is no one like him. Some of the older ones, like
A Small Town in Germany, are excellent. Just finished his second one, the one that came out right before he had his big breakout book
The Spy Who Came In from the Cold, and it is a superb whodunnit (although Smiley is in it). Shows his versatility, and it's about Eton, for the Anglophiles among us.
There's a new Clancy coming out soon. Those continue to be rewarding.
Bookmarking this thread for further suggestions.
Early Clancy books, especially the Jack Ryan series, were terrific, but the later ones are terrible.