Out in UK cinemas on 13 May is Father Stu, Mark Wahlberg's new faith-based movie and personal "love letter to God".

For Christians dissatisfied with the often highly sanitised and formulaic offerings from the conventional Christian movie stable, Father Stu will feel like a breath of fresh air.

It may be a faith-based movie but it is pitching at a broader audience than just the Church, and is infused with a gritty realism that makes it a far cry from the likes of God's Not Dead and Fireproof.

Among other things, there are sexual references and an allusion to pre-marital sex, it is profanity-ridden from start to end, peppered with coarse humour, and is at times violent.

Faith-based it may be; saintly it is not. And while for some Christians that will be just fine, for others, it may be a little more 'real' than they are comfortable with.

Directed by Rosalind Ross, Father Stu tells the inspirational story of real-life priest Stuart Long, a boxer with a dysfunctional background who must look for a new job and new purpose in life after injury forces him to hang up his gloves for good.

A crush on a Sunday school teacher leads him to church but in a surprise turn of events, what started out as a way to win her heart becomes a genuine conversion to Catholicism and this foul-mouthed rogue becomes a devout priest.

Yet, his life isn't about to get easier; it's about to get much, much harder and in one particularly powerful scene, Father Stu, facing the horror of a debilitating disease, weeps at the altar as he screams his frustration out at God. 

Christians will appreciate how honest Father Stu is about the ups and downs of real-life faith. If the prosperity gospel sells the lie that giving all you have to God will open up the door to a life of wealth and ease, Father Stu blows open that myth and reminds us that sometimes you can do all the right things and still end up in the hardest place. When that happens, what does faith look like then? Do we just give up on God?

Father Stu's answer to those questions is to cling doggedly to his faith and keep going against the odds, just like the real-life Father Stu who continued his priestly duties, despite immense physical pain and discomfort, until his death at the age of 50.

At its heart, Father Stu is all about redemption, overcoming obstacles and giving people second chances. It weaves together the good, the bad, the messy and the beautiful that are true of both life and faith, and gives room for the hard questions to be asked, while giving God a fair hearing. There is much to appreciate about this movie, but that being said, there's a reason why it's rated 15.

Father Stu is out in UK cinemas on 13 May.