At AA, we have three 'big' manuals and a bunch of smaller documents. Two of the big three are aircraft specific - the AOM (Aircraft Operating Manual) and ASM (Aircraft Systems Manual) - while the FOM (Flight Operation Manual) is not.
So let's say the visibility is low at our destination and we need to plan on a Cat III to an autoland, but none of us have done one in over 9 months. We'll dig into the AOM to review our callouts, required working equipment, what lighting needs to be available, and so on. It tells us exactly how AA expects us to fly their 777.
Last month we had a United jumpseater wanting to come with us down to Buenos Aires. We all know offline jumpseaters are not allowed on the flight deck for an international flight, but fortunately there were a couple of open seats in the back. That said it's a 10.5 hour flight and all three of us are gonna spend our breaks in the bunk - can this guy use our business class rest seat instead of being stuck in coach? We had no idea because we've never seen this situation before. FOM to the rescue! We were able to make it happen.
When I mentioned a low mins FO having a 15 knot crosswind restriction, that's also from our FOM, but not necessarily Endeavor's.
As for our ASM, sadly that manual doesn't get used nearly as much as it should.