Cryptonomicon
Cryptonomicon is an EPIC story (I'd call it Science Fiction under these rules) of the birth of modern cryptography, entwined with a treasure hunt and the beginnings of the internet. It is also historical fiction - it deals with real historical figures making important progressions.
In a 900+ page book, there are plenty of 'main' characters (with pithy summary):
- Lawrence Waterhouse - the day-dreaming crypto master
- his grandson Randall Waterhouse - UNIX/networking guru
- Bobby Shaftoe - brave/foolhardy marine
- his granddaughter Amy Shaftoe - tough talking diver
- Avi the entrepreneur - always has an eye on an angle
- Douglas MacArthur Shaftoe - no nonsense dad to Amy Shaftoe
- 'The Dentist' - lawsuit loving super-political-business-billionaire
- Goto Dengo - resourceful survivor
- General Wing - lucky realist
Set in World War 2, the Phillipines, Australia, America, and Europe (okay, set in most of the world from 1930 onwards).
Brilliant book, which I'd love to read again at some point, but will probably never find the time to tackle it all.
Also, see Neal Stephenson's 'Baroque Cycle' trilogy.