The Subtle Knife by Philip Pullman

I managed to read this book within the day ... and I have sought out the final book, The Amber Spyglass, from amongst the books on the bookshelf, this morning. Pullman introduces Will, from our own universe, who clambers through a window to another world, where he meets Lyra, also out of her world. In this world, spectres suck the concentration from adults leaving them listless, but they leave children alone. The two children are still interested in Dust, and Lyra meets with Dr Malone in WIll's world, who may be able to help them - in the final book. There are a few incidents which begin in this book but are not mentioned again - many threads to be tied up in the final book. Right, must go - I've a book to read!