Cryptonomicon by Neal Stephenson (1999)

The fact that this came out the same year as The Code Book must be some kind of serendipity, although I didn’t get around to reading the novel for another 25 years. I’ve now read a few Neal Stephenson books (mainly because I was casting around for science fiction to give my kids to read and ended up reading them myself), and for the most part thought that while they’re full of super-interesting concepts, on the character/story/writing front they were just OK rather than great—except for this one. It has a split structure where about half of it is set in World War II (largely concerned with events surrounding the Allies’ efforts to break the Germans’ Enigma codes and then make sure that the Germans didn’t find out that they did so, and featuring Alan Turing as a character) and the other half is set in the present day.

The two separate narratives are intertwined in multiple ways, which makes for a clever and satisfying structure, but the World War II parts specifically are just incredibly good. The present-day parts suffer a bit from the fact that the protagonist is by far the least interesting and least distinctive character in the book, which is admittedly unfortunate, but he’s surrounded by enough great characters—and the World War II parts are so phenomenal—that I’d recommend it anyway.