Absent other details, I'm going to suggest Eye of Minds by James Dashner, the first book of the Mortality Doctrine series.
Michael is a gamer. And like most gamers, he almost spends more time on the VirtNet than in the actual world. The VirtNet offers total mind and body immersion, and it’s addictive. Thanks to technology, anyone with enough money can experience fantasy worlds, risk their life without the chance of death, or just hang around with Virt-friends. And the more hacking skills you have, the more fun. Why bother following the rules when most of them are dumb, anyway?
But some rules were made for a reason. Some technology is too dangerous to fool with. And recent reports claim that one gamer is going beyond what any gamer has done before: he’s holding players hostage inside the VirtNet. The effects are horrific—the hostages have all been declared brain-dead. Yet the gamer’s motives are a mystery.
The government knows that to catch a hacker, you need a hacker.
And they’ve been watching Michael. They want him on their team.
But the risk is enormous. If he accepts their challenge, Michael will need to go off the VirtNet grid. There are back alleys and corners in the system human eyes have never seen and predators he can’t even fathom—and there’s the possibility that the line between game and reality will be blurred forever
The review here mentions three main characters, "Michael, Bryson, and Sarah", which would fit for the two boys, and specifically mentions the pain of being burned alive in lava. It is a fairly recent book, 2013. There is a CD version of it. I don't think it would have an audio-cassette version, unfortunately.