By Tad Williams. In four volumes.
I'd say this saga has been about 3000 pages in the reading. There are two major problems with this story:
The author doesn't, apparently, know how to be concise. 3000 pages is way too long. Couldn't he have taken out some of the detail? Please?
The science of about 50 years in the future is not very convincing. People are using palm readers as security (from what I've heard it's possible to fool fingerprint scanners now with about 15 minutes and some Jello), you can hack any system just as long as you're fast enough to get in before it throws you out, and VR rigs involving harnesses, hearing plugs and goggles can apparently hypnotize you into feel like you are in reality instead of the system and you can't disconnect. And also that you can die from what happens to you online.
There's another thing I don't like which is probably also a flaw: the author leaves the answers to almost all the questions raised (at least the big ones) to about the last 300 pages of the fourth volume. I mostly slogged through volumes two and three because I was afraid I would miss something, but I apparently could have skipped to near the end of the fourth volume and not missed too much. I would suggest that the author could at least have provided hints and clues about some of the answers (perhaps he did, and I wasn't smart enough to notice them).
Most of the threads (even ones I had forgotten) were wrapped up pretty well in the ending, although a couple questions were left unanswered. The ethical questions about the existence of the virtual life forms, one of the more interesting parts of the book to me, are never really considered in great depth. Most of them never even know and even if they're told, they seem to filter the information out as inconsistent within the simulation. Odd, huh? The Stone Girl (Vol. 4) is really likeable, too, and well characterized as a child.
One of the style oddities is the presence of a "Foreword" and "Afterword" in each book that I think should really be "Prologues" and "Epilogues." "Foreword", I think, implies more of an editorial note that is not part of the story's narrative.
I think the biggest problem with this story is its ridiculous length, but if you can slog through 3000 pages the author tells a fairly interesting tale.