The novels, in order of publication, are:
1) The Various, 2003
2) Celandine, 2006
3) Winter Wood, 2009
It's hard to describe these books without giving away huge chunks of plot; however, they are all concerned, one way or another, with the Various, a group of small people (who may be fairies, aliens, or what-have-you - nothing is ever made clear about their origins and nature, as we are given only their mythology and the other characters' interpretations of them to work with) who inhabit a virtually impenetrable area of dense woodland in Somerset.
If the Various are fairies, they are certainly not sweet, tiny and gauzy-wingèd; life in the Forest is, if not solitary or - usually - short, then at least often poor, nasty and brutish. Mostly they collaborate grudgingly and from necessity; the books demonstrate amply that prejudice and factionalism are not solely human affairs.
The books may be promoted as "Children's Literature", but if I had to compare them with anything else (always a tough task), what I'm most reminded of is Audrey Niffenegger's The Time Traveler's Wife. Not because of the subject matter - the only touches of romance in the books are in Winter Wood, where the protagonist's mother acquires a "sort-of" boyfriend, and, in what I find a most touching scene, we discover that Celandine, the protagonist's great-great-aunt, had a "very best friend" (and probably lesbian) relationship with one of her former schoolmates. There is also, as such, no time travel. What makes the connexion for me is the way in which the past and present of the series interpenetrate, with careful showing of how history and memory, not always easy bedfellows, are both necessary to a true understanding.
Perhaps the weak point of the story is that the plot, to some extent in the second book and almost completely in the third, runs around the Touchstone, which turns out to have been little more than a MacGuffin. Then again, it's quite possible that the author intended us to have no more understanding of the Touchstone's real nature than have the characters. It is, after all, a means to an end.
I'll certainly be looking out for more of Augarde's writing.