Terminal, the sixth and final instalment in the Tunnels series, was published in the UK in April 2013, and will be released in the US later this year. The Tunnels books feature Will and his friends' continuing fight against a terrifying and brutal subterranean race called the Styx, who want to take control of the surface. If you thought you were safe, you'd better think again.
A movie of the first book is currently being developed by Relativity Media in the US with Mikael Hafstrom as director. News of how it's progressing will eventually be posted here.
And Tunnels, Deeper, Freefall, Closer, Spiral and Terminal can be purchased here: