The latest chapter of my favorite iOS comic book app is here.

I’m talking about Upgrade Soul, a science fiction graphic novel developed for iOS by Opertoon.

Why is Upgrade Soul my favorite, you ask? Well, there’s the app’s impressive implementation of the Opertoonity engine, which delivers exactly what it says on the tin: fluid navigation, interactive 3-D, and dynamic music.

But let’s be honest, even the most fluid, interactive, and dynamic elements will be all for naught if they’re used to convey a weak story. Fortunately, Upgrade Soul has a pretty compelling story at its core.

If you can’t see the video embedded above, please click here.

Upgrade Soul is the story of Hank and Molly Nonnar, a couple of wealthy science buffs who decide to risk their lives for a second chance at youth.

And in Chapter 3, the latest installment of the graphic novel, the very thing that convinced the Nonnars to do what they did is finally revealed.

Like any other chapter in Upgrade Soul, Chapter 3 is available in-app for $1.99. You may also get it by buying or preordering Chapters 2 to 6 for the generously discounted price of $6.99.

Actually, if you’ve already availed of Upgrade Soul’s preorder bundle, you will immediately get Chapter 3 once you update the app.

Compatible with iPhone, iPod touch, and iPad running iOS 4.3 or later, Upgrade Soul is available in the App Store for $1.99.