The Portable Door by Tom Holt
It takes a little while to reach the part in this book that gives rise to the title, but once protagonist Paul Carpenter finds the portable door, we are taken on a fantasy journey that might occur if Harry Potter went to Narnia. Paul applies for a job as a clerk in a mysterious organisation and after a disastrous interview, is successful, although the Kafka-esque bureaucracy in which he finds himself working soon becomes more sinister than first appearances have hinted at.
The writing style is brusque and sardonic, the similes highly original, ranging from caustic (“the freeze-dried character laughed, making a sound like dangerously thin brake shoes”) to comical (“…then it struck him. As though he were Sir Isaac Newton and he’d just been hit on the head by a huge, scrummy toffee apple”).
Written in 2003, it does come across as a tad dated, but it’s an enjoyable read (with lots of plot twists) for those who love fantasy novels about goblins and time travel. To some extent it’s a surrealist novel. It’s also been showing on Stan so you might like to read the book to compare it with the adaptation.