The Keys to the Kingdom: Lord Sunday by Garth Nix

There is a strange house that is invisible to people who do not know it is there, and in it are those who rule time and days, creations of the Architect. There is one ruler for every day of the week, but for some reason, those creations have rebelled against their creator and nobody knows why.

Arthur Penhaglion, a formerly sickly boy, became the inheritor of the keys to the house, starting with the minute Key. In his climb up through the stages of the house, he has fought against, and won a token from each ruler of the days, from Monday to Saturday. In that time, he has made friends, but things have been going wrong in the real world, as the battle against the ruling Lords of the house spills over into the reality that the creator has made.

And while Arthur has made friends, his climb hasn't been without its costs as well. calling on the powers of the house has been slowly transforming him from wholly human into a Denizen, an inhabitant of the house. If he should become fully Denizen, he won't ever be able to leave the house again and invisible to his friends and family- and with the house disintegrating in the battle between Arthur and the Lords, if the House is fully destroyed, so too will the universe be, and everything and everyone that Arthur ever loved, gone forever.

Caught between a rock and a hard place, Arthur has no choice but to fight on and win, because the cost of losing is literally everything. But now his opponent is Lord Sunday, the greatest and most Powerful of the Creator's servants, the one who incited the other Lords to rebel. And Arthur's Denizen side is much more dangerous, violent and vengeful than his human self can ever be. But can he prevent himself from doing damage to his own allies as he becomes more Denizen and not human at all?

But even Arthur's allies may not all be on his side. As Arthur has been working to reconstruct the Will, the last piece of the Architect and Lady Primus, he must question whether the Will is really on his side after all, and if making it/her more powerful is the right thing to do. And can he ever return to his old life if he becomes ever more powerful and completely Denizen?

But first he must find the Incomparable Gardens, the domain of Lord Sunday. But why is his mother's house in the Garden? What does that say about him, Arthur Pehaglion, and will he ever uncover all the mysteries of the House and the Denizens? What will become of the Universe, and why was Arthur made the heir to the keys of the Kingdom?

Wow, what an ending to the series! There are many parallels to Christian thought and theology, with the Architect being the Creator God, and Lady Primus and the Will being like the Holy Spirit. Lord Sunday then becomes Satan, and the other Lords the Fallen Angels. The denizens, then are like either angels and other helpful spirits, or demons, too, considering some fight on either side of the conflict. And Arthur is the Jesus-figure.

But those wanting to read a strictly Christian take on this series will find some aspects rather troubling, though, if not downright distasteful. For starters, the Architect is female, and the reason for the rebellion of the Lords is not sheer willfulness, but because the Architect abandoned her creation and wanted to destroy it. Hardly Christian theology! The Lords wished for the Universe to go on, and Lord Sunday wished to take the place of the Architect, rather than letting the universe, and themselves, die.

The ending is both happy and sad. Even though the Universe is mostly saved, things will never be exactly the same. Arthur loses his mother, among other tragedies, leaving him and his siblings alone in the world. But he will never be sickly again, even if he returns to being strictly human, and the replacement for the Architect is keeping secrets from him... for his own good, of course.

This is a fascinating series that leaves me still wanting more. The ending is certainly leaving you with a question about what will come in the future when Arthur finds out about what the Architect has lied to him about. But it's probably more deserving of a short story rather than another series. I'd still be interested in reading it, of course. Highly recommended, both the book and the series.