Originally published in 1953, this book was selected for reprint as part of the "Fantasy Masterworks" series, so I thought I would check it out.
Holger Carlsen is a Danish-American engineer, who, while involved in a daring attempt to smuggle people out of Nazi-occupied Denmark, finds himself mysteriously transported to a medieval-esque land on the border of Faerie. He awakes naked, with no memory of how he arrived in this place - but finds a knight's steed and trappings sitting next to him, ready for his use, so he sets off on a quest to find a way to get home. Soon joined by an earthy little dwarf, Hugi, and a beautiful, nubile swan-maiden, Alionora, he experiences a set of adventures (in which his knowledge of engineering repeatedly comes in handy), faces the machinations of Morgan le Fay, and gradually comes to realize that his true place may be here, in this magical land.
It's a bit cheesy in parts, and suffers from some innate sexism (it was written in the 50's), but overall, a fun, light read.