Inkling is a very popular virtual textbook publisher on the iPad, and it recently spread out over to the web. Inkling now allows students to access their virtual textbooks from anywhere. The company is adding one more platforms to its collection – the iPhone.

The Inkling app is now universal, which means you can browse, buy and read textbooks from the iPad, iPhone, or the iPod Touch.

Inkling 3.0 brings the company’s extensive library of digital textbooks, cookbooks, and Frommer’s travel guides to the iPhone and iPod Touch.

The iPhone’s 3.5-inch screen isn’t exactly favorable for long reading sessions. This new app means that Inkling is primed for the release of the iPhone 5, which is expected to have a 4-inch display.

The iPhone app contains all features of its iPad sibling, including real-time synchronization for highlights and bookmarks, reading assessments, and an interface optimized for the smaller display.

The iPhone Inkling app also lets you download individual chapters from books, so you don’t have to waste space storing an entire title.

How much this will add to Inkling’s business is not known. Students mostly do their work on a computer or an iPad rather than on the iPhone’s relatively small screen.

But then many do their reading on their phones while out and about and maybe there’s an audience for academic texts in the same way.