That's not a bad strategy. When I plan a trip to place or region where I've been before, I loiter in book shops looking at every guide they have, looking up off the beaten path places I remember. Prices, if listed, are there as a guide to costs at the time of research. They're not intended to be accurate forever, or even spot on when you by the book. What they are, though, are generally accurate representations of price ratios relative to each other.
Good places go bad, bad places go broke.
Get what you need, not what's prettiest. Check the proportion of color photos to text to see if what are looking at is primarily a picture book with text or text complemented by pictures. Do your homework. Even if you have a loyalty to a particular guidebook series, check the competition is well. It's your responsibility to find the best book for your trip.