Binocular Highlights #1

My book, Binocular Highlights, has floated to the top of its category at Amazon.com. This is actually the second time since Amazon replenished their stock a few weeks back, so this ranking is no doubt partly due to some pent up demand. Still, it's nice to see. (For those of you unfamiliar with the book, you can look it over here at Amazon.com.)
I've been checking in on the Amazon.com sales ranking for my book regularly since it first appeared in late 2006. In that time it's popped up to #1 in its category (Books > Outdoors & Nature > Ecology > Star-Gazing) many times, but I have to admit I have no idea what market forces are at work here. The book will be #1 for a few hours, then sink down to #10 or lower, where it'll remain for a while before bobbing up to the surface again. (Probably by the time you read this it'll already have dropped down a few notches.) I've never been able to correlate these sales spikes with specific promotions, adverts, or even the phases of the Moon. I don't get it. But that's why I'm not in marketing I suppose.
I have a few copies with me that I'll be happy to sign and send to anyone who'd prefer to purchase directly from the author. Just send me an e-mail.
Thanks!
Gary