I'm not familiar with the work of Dan Brown, but I'll check him out...
On to the question of intelligent life...
I actually don't agree with any supposition that says it's difficult for intelligent life to exist. However, on the other hand, I'm also one of those people who believes that we have too narrow of a definition of "life-supporting."
It's not only popular belief, but also appears to be operating policy for space agencies, that if there's not some oxygen, then life can't exist. What a hoot! There's things that live on our very planet for which oxygen is a poison. Microbes that metabolize the harsh chemicals that pour out of deep-sea vents. Anaerobic bacteria that live in the steaming hot geysers of Yellowstone. Hell! How can we believe, with things like that around, that air is even needed? Okay, that last bit isn't serious. Life can't exist in a vacuum...
Or can it? Again, the assumption is made that living beings have to be biologically similar to us. What of silicon-based life? That theory's made the rounds before. For a fictional exploration of it, read Crichton's "The Andromeda Strain" or watch the 70s movie (I think it's better than the remake).
A living being mustn't necessarily metabolize oxygen, as pointed out earlier. Imagine a form of life that lives in the vacuum that draws its energy from the charged particles of the solar wind. Imagine a creature that lives in the crushing, poisonous atmosphere of Jupiter or Saturn.
Now, when you consider the other possibilities... when you realize that things musn't necessarily be like us, you must open your mind to the amazing diversity of life. Consider an intelligent being that has a control/memory system that operates on a totally different concept from us. For example, a crystalline optical brain complex. What about forgoing eyes, nose, and ears... our core senses... for the ability to sense electromagnetism and air currents?
All of these things are possible! So, you must ask yourself...
Would you want to tickle an eyeless space being with tentacle-arms that has a crystal brain in its stomach? This is to assume that its sense of touch allows for ticklishness and that it is capable of emotion. If it is capable of emotion, then the chance that it laughs is slim. It may change color or glow brightly.
Or die.
Who knows?