(Please note that this review is of the Swedish original, and not the very changed and edited English translation.)
This book is, as you might know, the first part of a series. This is noticeable, especially (but not only) to people who are familiar with the series since before. It's slightly more grounded and realistic than the other books; most of the recurring characters have still not entered the scene, and the plot is a bit less well-structured than the later books (at least if my childhood memories can be trusted). The ending is a bit too dependent on a contrived coincidence. Still, this is more of an adventure story than a clue-based mystery, and as an adventure story, it's not at all bad, though a bit more dull than I'd like at times, and the plot does take a bit too long to get going.