Keith Laumer 
Time Bender [EPUB ebook] 

Draftsmen can’t fight dragons.Then again, that’s usually no problem – they generally don’t have to. But Lafayette O’Leary does. When an accidental overdose of self-hypnosis wrenches him out of the dull (but safe) Mrs. Mac Glint’s Clean Rooms and Board and deposits him in the feudal, bedragoned world of Artesia, it takes him a little while to catch on, even with the attentions of the beautiful Princess Adoranne. Then he decides that he likes this new life of his – except for the part where he’s supposed to get killed…