If I had to pick a favourite book, I'd have to say any book from the Warriors series by Erin Hunter. I haven't finished the whole series yet (I am currently reading the fourth book of the third series) but there hasn't been a single book yet that I've particularly disliked. I just have so much fun reading the books! The feeling I get seeing all my favourite characters in the books mature and become essential parts of their Clan is indescribable. I'm not a huge fan of the third series right now but I still really adore it! I'd have to say my favourite books were from the second series. It was so action-packed and emotional.