To begin with though, it is a gripping, hugely enjoyable read! The basic premise is that when Lydia starts an online business, her closest friend Georgia wants to help so she sets up a fake Twitter account to pose as a potential customer. But then Lydia starts to confide in her new online buddy. And she reveals she knows that her best friend’s husband is cheating on her.

The plotting is really taut and page-turny, as well as being totally believable. I loved all the Twitter exchanges too — it felt very 21st century — and it has some real laugh-out-loud moments.

But, wearing my writer’s hat, the thing I found interesting was how Fallon switched half-way through the book (think Gone Girl) from Lydia’s first person p-o-v to Georgia’s. As a reader we really want to know whether Georgia knows Lydia is her new online friend (she does), and, if so, why she is taunting her with this information about her husband. And Fallon begins the second part by flicking to third person p-o-v. So whenever we are with Lydia it is first person, and whenever we are with Georgia it is third person.

It works really well. If Fallon had chosen first person for both it could have been confusing, unless she had labelled each chapter with Lydia or Georgia to signify whose p-o-v we were in, but I always find that a bit clunky and almost insulting to the reader. It is a simple trick that she pulls off with aplomb.

P-o-v’s aside though, it is a sharply written, hilarious, witty book about friendship and revenge. Just loved it.