The Goblin's Puzzle by Andrew S. Chilton*

The boy has no name.  All of his life he has been a slave.  As he journeys with one of his master's sons, he soon finds himself the opportunity to escape.  As he runs in fear, he encounters a goblin, two girls named Alice who both need rescuing and a nefarious Duke.
Readers who enjoy puzzles and logic will find this book delightful.
The author introduces logic terms after the story in a note to the readers.
*Highly recommend.
-Borrowed from the library.
Warnings/points to discuss: In the beginning, the master's son is murdered.   A man named Nikola brags about his romantic misadventures with married women (no details are given and limited to one page); The Boy points out that his parents knew each other very well if he was born.