Just like the first one I enjoyed the sightseeing trip, this time through Paris. I believe that the explanations on certain typically French things work well for younger, non-European readers but for me all the explaining was a bit too on the nose. But I'm not the intended target group for this on so it's easy to look past.
All in all I enjoyed Tunnel of Bones and am looking forward to find out where Cassidy & Jacob end up in the next book.