The web pioneer that missed chances to buy Google, Facebook, YouTube and Twitter faces questions about its purpose in a mobile world - and whether it is a takeover target

Marissa Mayer has just one year to turn Yahoo into a thriving, growing prospect - or else the venerable business will become an acquisition target.

That’s the thinking of Nicholas Carlson, a journalist whose book Marissa Mayer and the Fight to Save Yahoo! explores the company’s struggle under its charismatic new chief executive, appointed in 2012 to try to turn around a business that seemed to be sinking into despond.