The game is pretty straightforward and I didn't need a guide.
Hard to say exactly how long it took me to finish, but there were multiple sessions and probably took at least 4 hours or more. Maybe longer for me since I would reload/re-fight most of the harder fiends to figure out patterns and minimize damage before moving on.
As mentioned, there's a lot of dialog and cut-scenes to sit through that takes up a lot of time. Only skip-able if you manually turn them off before encountering them.