It's been said before on this very page, but Roy Keane is the most unique assistant manager in modern day world football -- everything he does is of interest to the great Irish public, no matter how trivial it might seem to outsiders.

Consider the past week as an example.  Last Friday, just after lunchtime and in a preposterous press release which claimed that the football biography will never be the same again, we learned that the great Roddy Doyle, creator of The Commitments, is to ghost-write Keane’s second book.

The work of art will be out in time for Christmas 2014, some 12 years after Eamon Dunphy put his stamp on the first account of Keane’s story in his own words.

Whatever about Dunphy’s use of poetic license in his descriptions of Keane’s controversial clash with Alf-Inge Haaland of Leeds United that seriously hurt the Norwegian’s career, there is also evidence that the infamous pundit used the Keane book to settle some old scores of his own.

That Dunphy and Keane are no longer on speaking terms tells you all you need to know about where their relationship went post-publication.

Doyle is a far more interesting choice as co-writer this time around for the mysterious and contradictory genius that is Roy Keane and for a book which will look at what happened next for Roy on and off the field post Saipan and 2002.

Quite a lot happened in fact. There’s his sacking from Manchester United and his rows with Alex Ferguson, his time with Celtic, his comeback with Ireland, his management spells with Sunderland and Ipswich, his reaction to Fergie’s recent book and his return to work as Martin O’Neill’s Irish assistant. And that’s just for starters in what promises to be an interesting account of a sporting life less ordinary.

There are some puzzling elements to all this as well. Quite why Doyle, one of the most successful writers of any generation, has nothing better to do with his literary genius than write a football book is beyond me.

Even if his publishers have already made the bizarre claim that the book, titled The Second Half, will combine “memoir and motivational writing in a manner which both disquiets and reassures in Roy Keane’s own original voice,” Doyle surely doesn’t need the money from such a project, one already met with great expectations.

This is going to be a book with a lot to live up to judging by the comments of its Orion publisher Alan Samson who claimed on Friday, “I believe The Second Half will become a benchmark for sports autobiography. The combination of an outstanding player -- and leader — like Roy with a writer of Roddy’s extraordinary gifts should result in one of the books of the year.”

What will make it a great book – and Doyle doesn’t write bad books – is the truth, something Keane has never been afraid of.

And yet I have to wonder how much of the truth he can divulge now he is in the employment of the FAI on a lucrative and binding salary.

His new job won’t stop Keane from answering the many claims made against him by his former United boss Ferguson in his best selling tome.

Nor will it cause him any problems if he wants to spill the beans on his time as manager of Sunderland and Ipswich and the parting of the ways at both clubs.

What promises to be intriguing is how Keane deals with any Irish questions this book may throw up, any reaction on his part to his dealings with the FAI over the last 12 years for example, or his post-Saipan experiences with Irish players, many of whom he had soldiered with previously and at least two of whom – Richard Dunne and Robbie Keane – he is now working with as Ireland coach.

If Keane is allowed to tell the truth, the whole truth and nothing but the truth by his FAI employers then The Second Half will be just as interesting to Ireland fans as it is to Manchester United supporters.  We’ll just have to wait and see how far he can go.

And while he’s at it, he might explain why he left the Middlesbrough-Charlton game 20 minutes early on Saturday and missed Shay Given’s best save in years.

That too made headlines on Saturday and Sunday, simply because everything Keane does turns to newspaper gold as Doyle is about to discover.

As for an alternative title for the book from Doyle’s own past, how about The Snapper – it makes sense in light of the Haaland story!

(Cathal Dervan is sports editor of the Irish Sun newspaper in Dublin)