What are the advantages and disadvantages of building a tablet / smartphone app in html 5?

I wrote a kids' storybook/picture book which I want to get made into an app for iPad, iPhone, and other tablets and smartphones.

I don't know much on the tech side of this.

I heard that it could be a good idea to create the app in html 5 and then 'wrap' it for each different device, rather than creating the app as a native app for each different device.

Are there any disadvantages to doing it this way?

I guess the main advantage of doing it this way, is that it's more efficient to build the app for lots of devices, but are there any other advantages?

Solution

Advantages:

"Write once and run anywere " is the main advantage of writing your mobile/table app using HTML5.
Build your app with open web standards to run on many platforms (e.g. Flash is a bad idea and even Adobe started supporting HTML5 in mobile devices over flash)
You can easily find developers with HTML, CSS, Javascript knowledge or you may already have.

Disdvantages:

Performance - Native application wins over HTML5 applications in this. But you don't need native performance for all applications. So its a disadvantage only in some cases.
Look and feel - Native look and feel is better than HTML5 app in some cases.

You may check phonegap, senchatouch, titanium.