Gripping and fun, two descriptors not usually seen together but I seem to keep describing Colfer's books with them! Colfer does this great thing where his characters are grumpy little shits and yet extremely loveable; Vern and Squib are no exception. 
Loved the lexicon use and location descriptions, they really made the swamp feel almost tangible and immersive. 
Only con is what I felt were excessive gory descriptions of injuries and deaths; they fit the plot but were on occasion shudder-inducing.