A Snarkling is gazing into his Kristal ball:
Over a year ago I submitted a ms to a midsized, reputable genre publisher. After several by-monthly emails back and forth--always very polite and prompt on their end, but of course they're swamped and quite behind--I learned my book had passed a couple of readings. I mentioned that I had the second book in the series finished and ready for review. The submissions editor there told me that it would help speed things along if I sent it in, so of course I scurried it over to the post office. They've now had that book for four months. My question is this: Do I mention anything of this situation in my queries to agents? Is it a hook at all, or is it basically like saying that I've already been rejected by one publisher?
Yes, you mention it. And you mention the editor's name. Not just "people at PublishOrBeDamned Inc. are looking at my tome" but "Herbert Snuffleuffagus is reading this, has had several readers and asked for a look at the second in the series".
Specificity here means an agent will know you aren't just blowing smoke. I've had people query me saying their work is being "considered" at FSG when what they did was send in an unsolicited manuscript and they haven't gotten the form rejection letter back cause they didn't include an SASE. You see the difference.
An agent may be more likely to give you time and consideration if it looks like MrSnuffleuffagus is serious about the thing.