Perhaps this shows me to be the geek I am: what first tickled me about Special Topics in Calamity Physics (besides the title) is the way Blue made all sorts of parenthetical references to literature, academic monographs, periodical articles and art. This actually is one of her most definitive actions as the narrator and main character--she constantly makes connections between events in her life (however small) to what she's read, most of which has been pushed on her by her father, ever the professor, since childhood.
Speical Topics in Calamity Physics is mostly mystery, but a couple chapters in, you'll forget that. Blue begins by telling us that she thought she had gotten beyond the nightmares of finding Hannah's body hanging, but clearly she hasn't, and so she's decided to write this book. This is not a type of beginning I usually continue reading, but Blue is such a wonderful character from page 1 that I almost didn't care. Blue isn't the only wonderful character, either--I got so lost in the rest of the characters that I completely forgot by page 100 how it was going to end. (The end in the beginning is, of course, not the end of the ending of the book.)
I also found it remarkable how disinclined I was to skip any part, even solely descriptive paragraphs, which is a testament to Pessl's writing. Every description was part of Blue's character development, and Blue is a narrator I couldn't get enough of.
About the mystery: readers are only reminded about two-thirds of the way through what the mystery actually is--not just who Hannah is, but why and how she died--and I didn't have any of it figured out till about 50 pages from the end, and then I was almost in a state of disbelief.
I'm still not entirely sure what I think about the ending--it's a little out there, it's brilliant, she's making it seem way easier than it should be--but the journey makes it well worth your while, whether you like the ending or not.