I'm coming at this from the point of view of someone who's watched all of the anime so far (the 14 original episodes and the two new ones that have aired this year so far) and will be watching the new episode later today. I'd read bits of the fan translated novels on sites like Baka-Tsuki but was always put off reading too much because I didn't want to spoil anything, preferring to get all the revelations from the anime.
The problem with this book isn't the source material (i.e. the original Japanese light novel) but rather the way in which it's been localised for western (well, American) audiences. While the Haruhi Suzumiya novels are indeed set in a high school, and while they are named after the heroine, it's a lot more of an ensemble piece and, actually, it's more like Kyon is the main character rather than Haruhi. Haruhi is more the "MacGuffin" of the plot (Wiki it if you don't know what it means) than the heroine; it's more about everyone else trying to keep her happy. As a silly analogy, it's like in the movie Speed. The main character is Keanu Reeves' character, not the bus. The bus is the MacGuffin - everyone else has to keep it from dropping below 50.
The problem is that this book, this translation and localisation, seems to be trying to make out that Haruhi is the main character. It turns it into something like Buffy the Vampire Slayer or Sabrina The Teenage Witch by setting up the story as "schoolgirl with superpowers!" and aims it at teenage girls. This mentality is only blatantly obvious in the blurb and general presentation of the book, but actually permeates every aspect of the translation. I won't say that the original stories are some deep metaphysical masterpiece, but they ARE a lot deeper than "hey girlfriend! Wouldn't it be, like, AWESOME to have, like, SUPERPOWERS!" It's a bit like if a foreign language translation of Red Dwarf tried to turn it into some wacky road movie in space.
If you want to read the novels, I'd strongly recommend you check out the translations on Baka-Tsuki; they're written more maturely, aimed at fans that appreciate the sci-fi elements and the versatile nature of the story (I mean, anything could happen, literally) rather than teenage girls who wish they were like Haruhi. They've also got way further than Volume 1.