I dont know if this really fits what you are looking for, but we had a Dutch writer called Thea Beckman who wrote the book Crusade in jeans (kruistocht in spijkerbroek). No clue if it was translated, and if it isnt too teensy, but I liked it when I was younger. It is about a boy from our time being sent back to the medieval times, and how he had to deal with the crusade he found there.