Natty went through the same change around 4 months. I think it's a common time for this to happen.
The main bit of advice I'd like to offer is don't worry about the books. I totally agree that they are just confusing!
Choose a technique that you're comfortable with and stick with it. (We stuck with settling in the cot, patting, 'shhh'-ing and if she got really upset, a cuddle, re-wrap and back in the cot again.)
Can you feed her to sleep?
Will she co-sleep?
What about a rocker or stroller during the day?
Good luck with it. I know exactly where you're coming from.