The Restoration Game by Ken MacLeod

This is a really difficult book to categorize. It's not exactly science fiction, more of a political thriller than anything, but it has an SF "wrapper". In the beginning of the book, a member of a future civilization, playing a highly advanced MMORPG, discovers that a group of Synthetic Psyches (AIs) have created a vast simulation, which turns out to be a Matrix-like reality that we are currently living. She also appears at the tail end of the book, to explain what's going on to the protagonist, hence the SF wrapper.

The heroine of the story is Lucy Stone, a Western girl who was raised in the tiny area of Krassnia, part of the former USSR. The area was once ruled by the Vrai, a race of warriors who claimed to be descended from the Romans, and who folklore says guarded a secret kept atop or inside a mountain, which each young adult Vrai had to experience in order to come into their full powers over the peasants in the area.

Lucy is now living and working in Scotland (MacLeod's homeland) as an admin for a game design firm who have developed an MMORPG with some novel features. First, it employs a novel game engine which allows it to run on any platform, even outdated systems with limited resources. It adjusts its graphics and physics engines on the fly, so to speak, and can display in any mode from 3D down to wireframe, without slowing gameplay. Next, players begin as members of a horde of orc-like creatures with primitive weapons, assaulting the stronghold of elf-like rulers of the land. If and when they win their way to the top of the mountain, they become rulers themselves, and turn about to find themselves facing a new horde of orc-like creatures, composed of all of the players who have newly joined the game.

One passage I found amusing:

"I found another hobby: role-playing games. In those days we played them around a table with rule-books and score-sheets made from paper. (You don't believe me? - Check Wikipedia.)"

It turns out that Lucy's mom has been involved with the CIA (and perhaps some other shadowy agencies) and used to pass information to them about the Krassnian region when they lived there. Her employers come up with a plot to use a game based on the Krassnian folklore as a clandestine forum where democratic dissidents can meet and plan their revolution against the Soviets. Lucy and the guys at her game company are recruited to adapt their new game to this template, which turns out to be not too much of a stretch, as Lucy has been central in developing its storyline and has subconsciously included most of the plot elements remembered from her childhood.

This novel has more twists and turns than a nest of pythons, and I enjoyed it quite a bit.