The book is about a guy (I'm fairly certain he is a no-success singer) who goes into a cabin in the woods and somehow ends up in another world.
At one point he sings with some elves or dwarfs or something, singing without words which feels right for him.
I also remember there being a love affair where the woman involved has bought some (ahem) "magical enhancers" but he says they won't need them. It's odd what you remember!
I think there are some weird kind of taxis too.