The Mortal Instruments is a young adult paranormal romance/urban fantasy, set in a colorful version of our reality where humans walk unaware of not just the vampires, werewolves and warlocks, but also demons and their part-human enemies - Shadowhunters. 
 The books are fast flowing with vivid characters, a lot of action, and 
 interesting twists. They contain: 
 * the use of magic, runes, and mixing of demon and angel blood with humans to create other species 
 * profanity (including the taking of God's name in vain) 
 * drinking (occasionally mentioned) 
 * violence (injuries, killing, and references to gruesome torture/death - although most descriptions refer to blood and are not gory) 
 * blood drinking 
 * homosexuality (ranges from knowledge of sexual preferences to physical displays of affection with individuals of the same sex) 
 * sexual content (ranging from kissing to making out/straddling in nothing but underwear) 
 There is also a theme of inappropriate romantic desires through the first three books. 
 See spoilers below for more details on the exact nature of the inappropriate romantic interest. 
 SPOILER ALERT 
 (view spoiler)[The first three books in the Mortal Instruments series focus on a young lady and young man who develop feelings for each other and then discover that they are brother and sister. While they do eventually learn that they are not siblings, there is some kissing and making out that occurs while they are still under the understanding that they are related. (hide spoiler)] 
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