Big news for fans of Eoin Colfer's teenage criminal mastermind Artemis Fowl – the author has announced that the eighth book in the series will be the last. The book will be out in spring 2012 but Colfer is keeping schtum about the title and the plot at the moment.

But don't worry, Colfer fans: it may be goodbye to Artemis but it's certainly not farewell to the Irish writer's riproaring blend of adventure and humour. He has also announced a whole new series, and will be delving into timeslip trickery for thrills and spills this time round.

Called WARP - an acronym for Witness Anonymous Relocation Program, used by the FBI to hide important witnesses in the past - the new series will feature a Victorian boy called Riley who goes on the run in 21st-century London pursued by a ruthless assassin from his own time and aided by a young FBI agent. Colfer has described it as "Oliver Twist meets The Matrix" and the first book in the series is due to be published in the summer of 2012.

Don't forget – members of the Guardian children's books site have the opportunity to meet and interview Eoin Colfer at the Guardian next week – check your latest newsletter for details, email us at childrens.books@guardian.co.uk for a reminder if you've missed it or check out the Get Involved page if you want to join to find out more.