I am not a Twilight fan, but I enjoyed Fallen. While the Twilight comparisons others have made are somewhat fair, given the focus on predestined love, they ignore one key difference: this book is actually pretty well written. The characters feel like real people (although we don't get to know a whole lot about Daniel - I suspect there's more on him in later books), the descriptions were generally original and interesting, and most importantly, I stayed with Luce for the duration of the story. The story was surprising but not overly so, and the plot twists at the end helped to make up for the slow-like-molasses first half. 
 So yeah, the pacing of the story is a little strange, and that was the worst element by far. I am still wondering why we needed those first 100 pages at all, except for character development. But regardless, it all comes together by the end.