Expecting Someone Taller (1988) by Tom Holt is humorous fantasy book set in the normal world that uses characters and devices from Wagner’s Ring Cycle. It’s a great premise and a good idea. Writers such as Neil Gaiman and Douglas Adams have explored similar territory with great results.
The book’s hero is Malcolm Fisher who accidentally winds up as the ring bearer. Various deities and gods then try and get the ring from him.
It’s not a bad book, but it isn’t really funny enough or clever enough to be great. It may also be that I don’t know the Ring Cycle well enough and that humour is really hard to do well in books. For anyone looking for something a bit different who has read all the Gaiman, Adams and others they can find it might be worth a look though.