An official guide to a bestselling series written by the author seems like a golden opportunity -- it's a chance for the author to reveal parts of their series that didn't make it into their original novels. 
 Unfortunately, "The Twilight Saga: The Official Illustrated Guide" doesn't come even close to living up to that promise. Most of the content is recycled stuff you could easily find on any Twilight website or wiki, and it's padded out with endless fluff, disingenuously dull interviews with Stephenie Meyer, and recycled factoids. 
 Yes, the first eighth of the book is devoted to Stephenie Meyer giving a prolonged interview to her "baffy," far superior fantasy author Shannon Hale. Basically the two women natter on aimlessly about various topics -- Meyer's books, the dream that got her started as a writer, her inspirations, her process, how wonderful Meyer is, blah blah blah. Most of it is nothing new. 
 There's also a brief Q&A about commonly-asked questions (some of which are REALLY unsatisfying!), cut scenes from the books, fan art, music playlists, profiles of the characters' CARS (I wish I were joking), detailed chapter-by-chapter plot points from the books, a timeline, and character stats and biographies for pretty much everybody in the series, including notable quotes, hobbies, and vehicles (what IS Meyer's obsession with cars?). 
 "The Twilight Saga: The Official Illustrated Guide" is a lot like the novels it describes -- lots of self-indulgence, padding and the occasional flickers of interesting information. Now, I will admit that there are some interesting new facts included here, particularly the backstory of Alice, Billy Black, and the Volturi, and some stuff about vampire wars, their divisions, their history. 
 However, that's about as good as it gets. Even with a whole guide to mess around in, Meyer's worldbuilding remains flimsy, the vampire origin/history is still horribly vague, and it all feels sloppy and halfhearted. Most of the book is either fluff (why does a GUIDE have a fan-art gallery?), or facts that were already revealed in the books (such as most of the characters' backstories). 
 There's very little consistency in the writing -- some character biographies are long detailed rambling affairs, while others are painfully short and vague. And there is almost no new content for most of the MAIN CHARACTERS. Would it have been so hard for Meyer to come up with a few pages of interesting stories for Rosalie, Edward or Jacob's histories that were NOT mentioned in the books? 
 Also... THE CARS. I am sick of them. I'm far more interested in historical vampire wars than I am in whatever Edward drives. But guess which topic gets more ink devoted to it! 
 Meyer also attempts to explain the biology of her vampires and werewolves more thoroughly... and fails miserably as she unloads one biological impossibility after another ("unbreakable" teeth, extra chromosomes, rigid cell membranes, etc). And there's the horribly racist implications of "everyone who becomes a 'perfect' vampire turns lily-white" -- interpret that as you will. 
 There are some interesting facts in ""The Twilight Saga: The Official Illustrated Guide," but the author doesn't bother to flesh most of them out enough. In the end, there's too little that is new.