Like the previous two volumes, this was highly entertaining reading and very engaging, and he actually ties things up somewhat for the major characters at the end, achieving an ending in some sense. But the ending is less than satisfying, because while the character's individual lives seem reasonably well wound up, he leaves us with some real ambiguity about issues in the wider world. And frankly, the more I sit here thinking about what I should say about the book and the whole experience of reading it, the less satisfied I am with how it ended.
So, if you read Cryptonomicon and loved it, you probably do want to read this series. It's enlightening, engrossing, and sidesplittingly funny. It's also insanely long, and one step below Stephenson's best work, so don't read it until you've read his other books and he's left you wanting more. And if you do read Quicksilver and The Confusion, you certainly will want to read The System of the World; in spite of what I said about the ending, it's still enjoyable reading.
8 out of 10.