In reading the quick synopsis of Brainrush, you're made aware that you're in for a different kind of thriller novel. Indeed, the story is an international, millitary-esque thriller but it expands into other genres as well ranging from sci-fi to paranormal and filled with bits of romantic and buddy comedy. To a large extent, this is a cinematic novel filled with lots of action and quick takes but it also slows down and plods through a lot of detail and information.
The premise involves a terminally ill man named Jake. During an MRI, an earthquake shakes the machine and rattles his body and mind and apparently unlocks some amazing mental and physical abilities. Before long, these abilities get Jake caught up in a global adventure with high stakes. The story continues to get more and more intricate with new threats and revelations showing up every few chapters. Many sections read like something caught between James Bond and Jason Bourne. As you reach the climax of the book and work through the final few chapters, you get a bit of X-files or Indiana Jones (and the Crystal Skull).
In terms of believability, the story stretches things as paper thin as many adventure movies. As such, the general character and plot development is a little weak, but an entertained reader can employ their suspension of disbelief to ride alongside Jake and his friends. As more and more outrageous plot elements showed up, I found my willing to suspend disbelief to be waning but I continued on and generally enjoyed the story.