Still, the idea of selling one work on the merits of another troubles me somewhat, and I want to know: what do you guys think about this sort of... referential marketing? Good, bad, or butt-ugly? And another thing. If we extend the question out a bit, how do reviews which make such comparisons sit with you?Here's the thing: I don't think referential marketing and review comparisons belong to the same camp at all. I mean, yes, they're vaguely similar in that they both require some kind of more popular book to support their claims. But referential marketing is marketing, and I would hope that comparisons slipped into a review stem from a critical source.
In general, referential marketing is cheap. It sells your book short, it's unfair to the author, and it's unfair to readers. Publishers need to be working to publish new and original books, and any move on their part to link new books to a more popular previous release (or as we see in this bizarre case, a reissue linked to a newer hit) is detracting from the individuality of the less-popular book. It's furthermore bad business planning - when backlash hits your popular book (and eventually, backlash will strike), readers may want to avoid books they otherwise would have gone for simply because of the association (I have often fallen for this kind of guilt-by-association...). And when the fad fades, you'll be left with a whole bunch of potential readers ignoring your individually worthwhile book because they assume it's just more of the same.
As for comparative reviews, I think the problem goes much deeper. Again we have the issue of having to rest the book up on a more popular crutch and not allowing it to grow individually, but this time there's also a clear benefit to the comparisons. In a critical review, a reader can gain a better understanding of the comparison. I'm not just casually tying The Hunger Games and Uglies without explaining why, I'm going into depth about the way in which both live in the dystopian subgenre. I'm explaining why I think these two books deserve to be compared. I'm using the comparison to highlight aspects of the book I want to discuss on a critical level. It's maybe not the best review style, but I can still find logical justification for it and often use it myself.
Then again, a review that doesn't actually go in-depth about the similarities and differences is probably no better than the referential marketing. It's never all black and white. On the whole, though, I feel we should tread these waters carefully. Just look where referential marketing can lead us.