I have read on numerous agent blogs about how they read an author's query, requested the partial five minutes later, requested the full two days after receiving that partial, then offered representation the moment they finished reading the full (taking only three days to do so).
My questions are these: Is that the norm for manuscript interest? Or is it more likely that an agent will take, say, four months or longer? And if it's the latter, what--if anything--is generally going on in those months aside from reading the manuscript? Provided the agent has verified receiving the manuscript, can an author read between the lines one way or another: He/she loves it? Hates it?
Sadly, I don't believe there is a norm. Some agents read quickly, others don't, and often times the speed of response is dictated by things out of the agent's control.
For example, for the past few months it's taken me FOREVER to read and respond to partials and full manuscripts. I'm still interested in all of these projects, but I'm just swamped with client issues that must come first.
Of course, there are a few agents out there that will read a partial or a manuscript and not like it, but choose not to respond because they don't want to have to pass on the bad news. They figure that after a year of no response the author will get the picture. This certainly isn't something I condone, but it happens.