Google and Sony announced today the launch of half-million public domain ebooks, optimised for the Sony Reader and for reading books on the go on your trusty old laptop.

Head over to the Sony eBook store – ebookstore.sony.com – and then click through to Google's Unearth a Classic section on the site to see what's on offer right now for absolutely no money at all.

Google is clearly on a roll this week, what with the UK launch of Google Street View and some rather tasty new Google Chrome browser experiments.

And if you are not (yet) the proud owner of a Sony PRS-505 or PRS-700 Reader, the experience of reading one of the half-million books on offer for free on your laptop is actually not that bad. Of course, it doesn't come close to the real thing, but then again, neither does the Sony Reader. Yet.

New Project Gutenberg?

"We have focused our efforts on offering an open platform and making it easy to find as much content as possible – from our store or others – whether that content is purchased, borrowed or free," said Steve Haber, President of the Digital Reading Business Division at Sony.

"Working with Google, we can offer book lovers another avenue for free books while still providing a seamless experience from our store".

Of course, free ebooks are hardly a new thing. Head over to good ol' Project Gutenberg if you want to see what else you can edify your brain with for free.