In an effort to explain (and define) my process for writing a book, I'm going to document what I do when trying to get to a recognizable end result.
The first 'draft' isn't really a draft. It's akin to note carding, where one takes a slew of notes and write them on note cards, and then determine the narrative from the facts that one has uncovered.
I do something similar, but instead of note carding, I use Scrivener to collect notes and digitally do the same thing that posting the note cards to a cork board will do.
At this point, I am a sponge. I take in and consider most reputable pieces of information, even those only tangentially related to the topic of the book. This will go on for months.
Once I get a fair bit of data, I look for a narrative. This narrative is never set in stone. When new data is uncovered, it has the potential to update and even upend the flow of the story I think should be told.
Once the narrative is found, and once I feel confident in the story the book should be telling, I establish this as the baseline of the book. This is the research draft. Once it's established, I spend the next several drafts tearing it apart.