Confused over how to spend those book tokens you got for Christmas? Fear not, help is at hand in the form of a new study of the Ulster Unionist Party, written by a group of academics who previously produced a similar book on the DUP. Well, authors do love a good sequel.

The Ulster Unionist Party: Country Before Party? is selling for a hefty £60, so it's safe to say it's intended more for libraries than the general reader, but it does pose some important questions - namely why, despite being on the right side of history by backing the Good Friday/Belfast Agreement, has the UUP gone from being the historically dominant unionist party to looking as if it's in terminal decline, and what, if anything, can be done to stem the tide?

The authors began the search for answers by conducting the first ever survey of grassroots members. One thing they found is that UUP members generally agree with the DUP on an Irish Language Act, with just 4% believing that English and Irish should have equal status in Northern Ireland, while only 29% back same-sex marriage.

Also worth noting is the "loathing" which many harbour for that same DUP, a hangover from Rev Ian Paisley's time. One of the book's authors, Professor Jon Tonge, said: "Most UUP members we interviewed spent more time criticising the DUP than they did Sinn Fein."

He believes there's still a chance for the UUP to claw back some of its old relevance, but in order to do that, it needs to reach out beyond its traditional base and attract support from those who have not traditionally found a political home there, including Catholics.

Catholics who either support staying in the UK, or who are unenthusiastic about the uncertainty which a united Ireland might bring, have become something of an endangered species since the Brexit vote forced everyone back into their bunkers, but they do exist and one striking finding from this new book is how few have been attracted to the UUP.

There are actually more of them in the overtly Protestant-friendly DUP (0.6% of whose members identify as Catholic) than in the more centrist UUP (0.3%).

Could it be that these are conservative Catholics, tactically getting behind the DUP's hardline stance on abortion and same-sex marriage?

Whatever the reason, in both parties you can still "count the Catholic members on the fingers of your hand", as Professor Tonge puts it bluntly, and perhaps it's overcomplicating matters to see that hardly surprising fact as needing explanation at all.

People generally support parties which they perceive to be on 'their' side. It's intuitive and unconscious, rather than strategic. There aren't many Protestants in Sinn Fein, either.

So, should we just accept that politics in Northern Ireland will always be divided on sectarian grounds and stop trying to reinvent the wheel politically?

For unionists, inconveniently, that's not really an option. The imminence of a united Ireland may have been giddily exaggerated by nationalists in the past while, but there's no room for complacency.

If Northern Ireland's place in the UK is to continue, long-term, it's essential that both unionist parties forge an appeal to Catholics - and they're just not doing that.

Partly, that's a result of the stand-off around the dissolution of Stormont, which means that electoral rewards flow to those who exploit divisions, rather than heal them.

It could be that unionists just don't believe there's any point trying to appeal to moderate Catholics right now, but that's short-sighted. There surely are Catholics who, despite their instinctive cultural Irishness, might be persuaded to stay in the UK.

The short-lived NI21 party sought to open the door to them, with a platform described by former deputy leader John McCallister at the time as "pro-UK, but not in favour of loud, down-your-throat unionism".

Tina McKenzie, former NI21 chairwoman, is a Catholic from west Belfast and daughter of a former IRA man. She put it this way: "If people asked 'was I a unionist?', I would say no. But if they asked if I was for Northern Ireland staying in the UK, I would say yes."

Many stuck in a facile, binary view of political identity probably still find that distinction bewildering, but it describes a real position on the political spectrum. That she's no longer involved in politics tells its own tale.

It's initiatives such as this which Professor Tonge is surely suggesting when he advises the UUP to develop a "more positive agenda" based on "an inclusive, non-sectarian and fresh unionism which is constitutionally robust".

Even if the numbers of Catholics who'll ever make the leap to actually voting for such a package will always be small, it's symbolically important to be seen to reach out to them, but it's as if unionists simply can't summon up the extended enthusiasm to do so.

DUP leader Arlene Foster has made some significant gestures of reconciliation, not least her attendance at Martin McGuinness's funeral and her trip to last year's GAA Ulster final, where she stood for the Irish national anthem.

Unfortunately, without getting back into that whole 'crocodiles' debacle, she has a tendency to then throw away every bit of progress made with a thoughtless outburst of irascibility.

That the DUP keeps finding itself facing charges of being anti-Catholic is, in part, testament to Sinn Fein's success at demonising their opponents, but there is a definite subset of unionism - over-represented in the DUP - which has allowed a legitimate hatred of Irish republicanism to warp into antipathy for Irish identity and culture itself.

The late Rev Paisley blurred those lines between religion and politics, and the shadow has never been fully lifted.

The UUP needn't be so smug about that, either. In this new book, only 39% of UUP members say they "would not mind" if someone in their family had a mixed marriage, with 32% saying they would mind "a little" and 25% saying they'd mind "a lot".

That's genuinely depressing. What is Northern Ireland if not a mixed marriage writ large? Walking away from the Republic, or the UK, may be possible, but we can't divorce one another. If anything, it underlines that bigotry here still tends to be expressed in religious terms in unionist circles and in political terms in republican and nationalist circles.

Perhaps one is as bad as the other; perhaps, ultimately, they're even the same thing. But until unionist parties really understand the optics of how they address those outside their own community, both are doomed to remain, in Professor Tonge's words, "beyond the Pale to Catholics".

The Ulster Unionist Party: Country Before Party? by Thomas Hennessey, Maire Braniff, James W McAuley, Jonathan Tonge and Sophie A Whiting is published by Oxford University Press

Belfast Telegraph