In addition to the other projects I have going I'm working on a non-fiction, true crime book right now (more details on the topic later).
Several people at the various locations where I've obtained research materials have asked how much time I research a book before I write it and the answer is always "as much as it takes".
As you know if you're a fan, most of my work is fiction but even in those there is so much research involved it is unbelievable. A historical fiction novel I'm still working on, Louisiana, takes so much research time that it seems like for every hour I write I spend 5-10 hours researching, and that's probably a low estimate. I have books scattered everywhere on various time periods in Louisiana history as well as piles of photocopies stacked within reach of my desk.
The true crime book, however, makes the research on the others pale by comparison. I have over 30,000 pages of material in PDF format, with another couple of hundred to scan, and hours of video and audio on the topic. And that's just what I have right now. I still have Open Records Requests out to various government officials and agencies which could easily add thousands more pages.
Yes, I do read every line of every page of research. One of the lessons I learned back when I was a young lawyer was the importance of knowing your topic and the evidence inside and out. I remember one case where the other side produced 20k+ pages of documents and I read through everything 5 times before we got to trial. Very quickly it became apparent that the other side hadn't been as diligent since they had no idea what kind of a "gold mine" their disclosures were to our case. No matter what they said on the witness stand we had a document saying the opposite.
My legal background is helping a lot with researching this true crime book since it makes it easier to spot when something is missing or when it isn't what the "authorities" said it was.
The other way the legal background helps is you are trained from law school onwards to enter any case with an open mind, letting the evidence take you to your conclusions rather than you deciding what happened and then looking at the evidence in that light.
I hope to have more for you soon on this book, since it is a really interesting, although tragic, case.