The Last Apprentice
Out of all these books I have never had a nightmare or been slightly scared by any of Joseph Delaney's stories. I can think of only one other book that bothered me like this is Darren Shan Demon Series.
Slither breaks away from the main characters of the Last Apprentice and introduces a few new ones. Slither being the main. Slithers world is interesting, his thoughts and what he holds himself too are interesting. His world is also terrifying and I do not understand why the humans have no migrated away.
Nessa is also an interesting character. She is afraid, but gets past it at key moments but has consequences for moving past the fear.
I am very curious to see how both characters will grow and mature in the next few books. I thought this was the last book in the series turns out it's not. Guess I have more books to buy! :)