koboIt looks like investors think there’s real money in e-reading — at least, judging from the $50 million round just raised by e-reading startup Kobo.

The company offers its own e-reading devices (the Kobo eReader and the Kobo Wireless eReader), as well as apps for a wide range of other platforms, including the iPad, iPhone, Blackberry, and Android. It has also partnered with Samsung, Research in Motion, and HTC to supply the e-reading application for their tablet devices.

And even though it may be less well-known than competitors like Apple (with its iBooks app) and Amazon, Kobo seems to be growing fast, with 3.2 million users, including 1 million added in the last 90 days.

The round was led by an undisclosed institutional investor, with funding also coming from past backers Indigo Books & Music, Cheung Kong Holdings, and others. Toronto-based Kobo said it wants to use money to expand internationally (last week it announced plans to open localized versions of its e-book store for Germany and Spain) and to launch new products.

This is the largest round I’ve seen for an e-book company, but the area has already attracted some leading investors. For example, digital textbook maker Inkling’s investors include Sequoia Capital, while Callaway Digital Arts, which creates e-books that are enriched for iPads, has raised money from Kleiner Perkins Caufield & Byers.

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