I just found out about this book, it's called Conceptual Physics and is written by Paul G. Hewitt.
Google BooksIt seems pretty interesting, doesn't really use maths that much and instead focuses purely on the theory aspects. The writing style is really informal (which can be a disadvantage). It looks like it'll be a good supplement and an interesting read. It seems to be for first year
introductory physics, but it's really easy to understand from what I've read so far (so for the overlapping topics, it will go a bit beyond our level, but not that much). I'll probably give it a good read soon (it has a chapter on Sound, Light and E&M). The exercise questions are theory/explain type questions as well. It would be good practice for theory questions, trial exam theory questions are nearly always dull and pedantic.
Melbourne University has a few copies of various editions, it would be worth going there and taking a look at this book. There is a High School version as well, don't know what that covers. I wouldn't be surprised if other libraries have copies of it. You could also "borrow" it from the internet.
edit: After reading some of the chapters, it does explain physics nice and simply and focuses on concepts. The review questions are really basic, but the exercise questions are pretty good. I didn't realise this at first, but it's quite obvious it's for people with no physics background. However, it does go beyond our course (covers A LOT of stuff that we don't, e.g. it does go into general relativity and other uni physics topics) and provide light on a few topics that the VCE textbooks don't explain that well. So yeah, I think it's a good reference to get an initial understanding of the theory (pretty important for Unit 4), and would be worth borrowing for like a week and reading through it. Personally, I wouldn't waste money on it (unless it was like under $5). Don't expect too much depth, the explanations are on-par with the level our VCE textbooks explain it (but with a coherent writing style).