Disclaimer: I have no real opinion on Hilary Duff. I haven't heard her music, and my only exposure to her movies was a two-minute cameo in Human Nature. Too bad her debut book is a lackluster limp lump of lifelessness. "Elixir" isn't a devastatingly bad paranormal romance, but it is crammed with cliches, clumsily written, and has a protagonist so Mary Suish that it burns. 
 After a vacation trip across Europe with her friend Rayna, Clea Weston discovers that a ageless hot guy has been stalking her across Europe. He's also in all photographs of/by her, and she's having dreams about past lives with him. And during an otherwise pointless trip to Rio, she finally encounters the man, who is named Sage. 
 Sage turns out to be connected to Clea's father, who has been presumed dead for months, and the Elixir of Life he was searching for. And after discovering her father's data on the Elixir (courtesy of REALLY IMPROBABLE GUESSES), she and her friends Ben and Rayna accompany Sage on a... very leisurely quest to discover the truth. 
 It feels like someone told Hilary Duff, "Paranormal romance is hot right now! Just write a plotless book with a bland heroine, sexy boys, and some supernatural stuff!", so she dashed off "Elixir" over the weekend. This is one of the blandest, most cliched paranormal romances I have ever read; it feels like it was made with Mad Libs. 
 Part of this is because Duff's writing is terrible -- her style is as bland as cold oatmeal, and it's full of leaden infodumps, repetition (Sage is always "magnetic!"), and cheesy descriptions that are trying to be poetic ("endless swirling mass of inky black nothingness"). And the dialogue will make you want to claw off your ears, especially when Duff tries to be romantic or funny ("Wow. He must spend a fortune on eBay"). 
 To make matters more confusing, Duff stuffs the story with all sorts of confusing, inconsistent stuff about fate, and pads it with pointless scenes that add nothing (time to talk about cinnamon buns, sex and clothes!). Even worse, half the supernatural concepts in here like the reincarnation and the incubus/angel theory are TOTALLY NEGLECTED. They contribute nothing! 
 Finally, the ending is confusing, anticlimactic, and solves nothing... which means a sequel is probably is probably in the works. 
 Clea isn't as repulsive as many paranormal romance heroines... but she's still boring and immature. And even worse, she's a Mary Sue -- a wealthy yet humble girl who also happens to be a globetrotting teenage photojournalist. And a worldwide megacelebrity. AND a Krav Maga expert who becomes helpless at convenient times. Does she also sing like a nightingale and have rainbow hair? 
 Sage is basically a blank slate with "Mysterious Love Interest" stamped on his face, and Ben is just pushy and annoying. Almost all the other characters are devoid of personality, and even the antagonists -- who have the ridiculous name "Cursed Vengeance" -- are totally faceless. 
 "Elixir" is a paint-by-numbers paranormal romance, with no passion and not much of a plot. Hilary Duff, please stick to singing.