You can't claim a book is "heating up" without looking at historical sales data. Number of bidders and number of watchers shows interest, but tells you jack squat about where a book is in its sales cycle.
I see Lyria as a tool to understand what's selling. It's a snapshot of the moment.
Well, anything with bids (and no reserve) is going to sell ... I see it more as a list of items that garner a certain amount of attention when they're listed on eBay.
But, again, without historical data, it doesn't tell me anything more than that book X has Y number of bids and Z number of watchers. Does this mean a higher or lower ending price than when the last copy of book X was listed? There's no way to tell.
Isn't that the definition of something that's heating up?