Pros:
- the most original fantasy world of this day and age with great execution
- Complex characters with understandable and realistic motives
- Cohesive and gripping story from beginning till the end
- You can notice art developing significantly through entirety of the title (both quality and originality)

Cons:
- Main Character for the first half of story is one-noted and annoying
- There may be too much coincidences even for supernatural fiction

It's a shame and a blessing that this manga got also one of the best anime adaptations. It's not obvious choice which should you pick first.

There is huge chance that this series may become your number one even if you have read Death Note (I'm really trying to fill the review and not to bore you)