I did E Lit at 'O' levels 2 years ago, the same book as ladyintears, TKAM. I think you're a bit unlucky in that you're doing a relatively new book, because for an older book like TKAM:
1. Teachers have taught the book many times before, hence they're more likely to get the 'teaching formula' right
2. There are ample guidebooks available (i used the 2007 Cliffnotes guidebook and my mum's 1971 guidebook LOL)
3. There are many people out there who've done it, and are able to offer you help
4. There are only so many questions Cambridge can set without having to reuse. Hence its easier to spot questions and themes
However, for me, combined humans was always a just-pass or fail subject. My SS was absolutely terrible, i hated it. Lit was my saving grace, i often got A1s. I guess its always first and foremost knowing your material. Lit requires you to know your material, then to formulate arguments/opinions based on the situations. You need to know which opinions/arguments apply to which situation and which are irrelevant. You also need to know how far to argue, i used to go too in-depth, where spending the time used to further the argument could've been used to argue another point, of which the latter would have gotten me more marks. Perhaps that's your problem.
Or, it could be the more common problem of 'I don't know what to write.' There's no magic formula for this, i was always good at bullshitting though, and the things i wrote usually got me out of jail whenever i didn't know what to write. I even bullshitted during 'O's itself. If you're doing well in english, this shouldn't be a problem.
Oh and did i mention that i got A1 for combined humans in the end? Hahahahaha. My SS failed all the way to prelims. I'm so thankful that it all somehow turned out well in the end. I regret not being able to offer more info here, i'm now a science student, the only 2 humans related subjects i take are econs and GP. However, i hope that all i've said helps in one way or another. And feel free to correct me if i'm wrong. Enjoy your 'O' level year man, if ya go into JC its gonna be a drag. Cheerz!