Our Lady Of The Forest by David Guterson.
Ann Holmes has had a problematic adolescence - repeatedly raped and eventually impregnated by her mother's violent boyfriend, she has fled (via an abortion clinic) to the run-down former logging town of North Fork, Washington, where she now lives in a tent in a campsite on the outskirts of town, scratching a living foraging for mushrooms in the damp woods surrounding the town and selling them. Otherwise she passes the time hanging out at the campsite smoking dope and occasionally indulging in a few "special" shrooms, the ones you don't generally make risotto with (unless you throw awesome dinner parties).
One day while foraging in the forest she has a visitation from the Virgin Mary, who among the usual turn away from sin, be excellent to each other stuff makes some specific demands about building a church in her name on the exact spot the vision takes place. At least this is what Ann reports to her friend Carolyn back at the campsite; Carolyn is a bit more sceptical about the whole thing. Not everyone in the local community is, though, when word gets around, as it inevitably does. Ann's daily pilgrimages up to the spot where the first visitation occurred acquire a motley band of followers, and the local Catholic Church start to take notice, primarily in the person of Father Collins, a young-ish priest not so institutionalised that he is immune either to doubts about his beliefs or indeed to the charms of a young teenage girl looking to him for guidance.
Times are hard in North Fork after the logging industry died off, and it turns out people are pretty keen to believe - people like Tom Cross whose son has been in a wheelchair since a tree fell on him in a logging accident and who now ekes out a living at various part-time jobs while hanging out joylessly at the local bars and occasionally breaching the terms of the restraining order his wife took out against him. Some take a more pragmatic approach to the whole situation - Carolyn's initial scorn gives way to a realisation that there is money to be made, and she assumes the role of Ann's spiritual guardian and chief co-ordinator of the collection buckets, buckets which fill up pretty quickly when Ann's fame spreads over the internet and thousands flock to North Fork.
Things come to a head when it becomes clear that the timber company who own the patch of forest where the visions occurred aren't just going to hand it over for someone to plonk a church on it, and moreover aren't all that happy about thousands of people traipsing up and down every day trampling the undergrowth and shitting in the streams. Ann's health is also deteriorating; she suffers from asthma and various other respiratory complaints and the constant kneeling in a damp forest isn't helping. The Church have also sent one of Father Collins' superiors down to investigate Ann's claims, and Tom Cross has developed an increasingly manic fixation on getting Ann to perform a miracle and cure his quadriplegic son. A climactic confrontation occurs, following which things resolve themselves, not perhaps in the way anyone had foreseen, but in a way which could be viewed as fulfilling the prohetic words in Ann's visions, depending of course on how strong your need to believe is.
No doubt this can all be read a number of ways depending on your point of view, and no doubt that's the point of it - to me there's quite a bit of broad satire of the sort of people who buy into all this nonsense and mooch around bovinely clutching phials of holy water and relics (with the obligatory link here), but also something a bit more serious about how poverty, hardship and misery breed exactly the sort of conditions where people will clutch desperately at anything which might offer a way out or at least a glimmer of hope that things might be better, however implausible and absurd it might be, and about how organised religion brutally siezes and exploits this to further its own ends.
I read Guterson's Snow Falling On Cedars (later filmed) a few years ago and thought it was excellent, so much so that the two books of his I've read subsequently, East Of The Mountains and this one, pale slightly in comparison. Where all the books are very good is in their evocation of the landscape in which it all takes place; in the case of both Snow Falling On Cedars and Our Lady Of The Forest this means the Pacific Northwest and Washington state in particular - lots of forest and moss and sea mist and general chilly dampness. Where the later two books fall down in comparison with the first one is in being a lot more loosely plotted and meandering; no doubt this is the norm and the strong narrative drive provided by the courtroom drama that forms the background to SFOC is the exception, so I guess it's just down to which order you read them in. Nonetheless if it's advice you're after (and why wouldn't it be?) then I'd suggest Snow Falling On Cedars is the one to go for.