It's been a while since I read it, but the novel Requiem involves Picard being thrown back in time to Cestus III right before the Gorn attack in Arena. Since he's alone and cut off from the Enterprise, it spends time in his head, though part of it also deals with him trying to decide whether or not to break the timeline and try to prevent the massacre, if I recall correctly.
There's also the TNG entries in the Dominion War subseries that have Picard on a covert mission in Dominion territory. And there's the excellent The Buried Age, which is about Picard's life following the loss of the Stargazer leading up to his taking command of the Enterprise - this one, actually, I can't recommend enough.