Flash is an interesting one-man-against-the-world story but ultimately falls short as the world doesn't quite support the plot. Still, an interesting read.
Jonat deVries is an ex-Marine colonel who resigned after running one too many missions for a government doing the bidding of heartless multinational corporations. He founds a consulting firm that specializes in analyzing the effectiveness of emotionally charged advertising, and then discovers the newest contract he has is a setup. The story basically revolves around his attempts to discover the why, what, and who of his enemies, the use of his spec ops training to destroy them, and how he falls in love.
The fact that deVries is a full adult protagonist is a nice switch from the typical Modesitt junior officer pilot, as well as the fact that he ends up having to deal with family issues - something none of Modesitt's heroes outside of the Spellsong series have ever faced. Modesitt is clearly trying to break out of his formulaic rut, and the plot as a result is better than his last few scifi ventures.
The problem - unusual for Modesitt - is that the world he builds up doesn't quite support the characters. Part of the problem is that the predecessor Archform: Beauty was an interesting exercise for Modesitt in writing 5 separate characters, but the world built up was not particularly well fleshed out given how much the plot shifted around. Flash isn't helped by this. We're still not really sure what happened to cause the ecological disaster that changed the world, how humanity recovered, or for that matter how the technology that deVries analyzes affects people. Modesitt usually gets away with ok plot writing by making a really interesting world; in this case, the plot is above average but the world isn't. Modesitt does a nice job as usual with ironic political observations; as in the Ghost series some of his most powerful observations come from the alternate world he creates.
Still, an interesting read and better than average...just not worthy of 5 stars.