Lexicon can be best summed up with the idea that "words have power." More specifically, if you say the right words, you can bypass all the filters and make someone very compliant or agreeable to what you want them to do. If you watch Vampire Diaries, it's similar to the idea of compelling someone.
Lexicon starts right out the gate (at an airport) with some fast-paced action and it doesn't really let up. Multiple groups are trying to kidnap Wil from each other for some reason all the while he pleads they've got the wrong man. At the same time, a runaway is being recruited to a mysterious school where they're taught all kinds of subjects from professors who all use the pseudonyms of poets. The studies range from psychology to history and as they become more advanced, some rather interest linguistics courses, as well as studies on demographics and profiling. As it turns out, everyone fits into a particular category and being able to identify a person's category you're able to learn certain words or catch-phrases that will allow you to control them. These words are like secret codes or backdoor computer code that grants you full access to the system.
Somehow, a town in Australia is key to it, but everyone in the town is dead and anyone who enters the town ends up dying. Not to get all Reading Rainbowy on you, but if you want to know more, you'll have to check out this book. Lexicon is suspenseful, funny, fast-paced, with enough puzzle and mystery to make you wonder "what's next?"
Definitely difficult to put down. A very fun read.