Every 青の祓魔師 [Ao no Exorcist] (Blue Exorcist) book in order by Kazue Kato, 5 in total. VibeReads ranks and describes books by how they feel to read, so you can see what each instalment is actually like before you commit to the series.
Get a copy: AmazonBookshop.org
Get a copy: AmazonBookshop.org
Get a copy: AmazonBookshop.org
Get a copy: AmazonBookshop.org
Get a copy: AmazonBookshop.org