What's the difference between Invisibles: Countdown to the Millennium, and Invisibles: Invisible Kingdom? I thought there was only one volume-worth left to collect?
They are the same book, I think Amazon had it down as Countdown..., but the final title was actually The Invisible Kingdom. If you're ordering online, go with Kingdom.
That said, Amazon.co.uk still have 'The Invisible Kingdom' down as not yet published, but they'll let you order 'Countdown', so you might want to go for that 'un. Someone here said they'd done that and received 'Kingdom', no problem.