Amazon Upgrade — 'Read your books online'

What's this?

Last evening on Amazon I happened on this new — at least to me — feature.

And since not a day goes by that I'm not on Amazon for one reason or another — to buy something, find out about something, grab a picture for a post, etc. — I have to believe it's a relatively recent addition to the site.

Long story short: You almost wouldn't notice it (can you find it below?),

but it says "Upgrade this book for $7.59 more, and you can read, search, and annotate every page online."

Turns out I've previously purchased six books over the past 10 years eligible for an upgrade, at prices ranging from $1 to $5.60 for the additional features.

Interesting.

Somehow this is meant to compete with Google Book Search but I don't see how it's possible to compete with free.