The Subtle Knife by Philip Pullman

The thrilling second book in Philip Pullman's His Dark Materials trilogy, read by the author and a full cast.
In this stunning sequel to Northern Lights, the intrepid Lyra Silvertongue and her daemon, Pantalaimon, find themselves in a shimmering, haunted other world - Cittagazze where soul-eating Spectres stalk the streets and wingbeats of distant angels sound against the sky.
Here she meets twelve-year-old Will Parry, a fugitive from a third universe. Will has found a small window between Cittagazze and Oxford that brings him into this strange new realm.
Will's father, an explorer, disappeared years ago, but recently some odd characters have started asking questions about him, and now, having accidentally killed one of them, Will is wanted by the police.
Armed with the subtle knife, a tool that cuts any material (including that which separates universes) and Lyra's alethiometer, the children set out to find John Parry, with adults of various stripes in desperate pursuit. From Goodreads.

This is really good. This was a re-read (listen) for me but it is so long ago since I read it that it seems new. I am also enjoying this special audio with all the different voices for the characters.
Lyra and Will become friends and have to survive together. Luckily they get help from Lyra's friends. 

This book qualifies for:
You Read How Many Books? Reading Challenge 2014
Crazy Challenge Connection - Oktoberfest
Goodreads Reading Challenge 2014
Crazy Challenge Connection Bard of Avon
Crazy Challenge Connection 2014 RaT #9
FrightFall Read-a-Thon 2014