Beset By Demons by Kaje Harper

They’ll take a leap into the unknown to protect the world.

There’s something seriously wrong with Earth’s magic. A demon has appeared unsummoned out of thin air, familiars can’t return Home, and as Grim points out, rats smell like summer in the middle of winter.

Grim and Pip can deal with rats; Silas can banish one wayward demon. But soon there are other demons, more each day, and Silas’s old mansion is full of mysteries. He and Darien will need their familiars, their friends, plus a whole lot of luck, as they search beyond Earth for the forces that have changed their world. And to have any chance of getting safely home, Silas will have to confront a past he’s avoided for ten long years.