Should I get the optional book for Accounting and Finance?

I am doing Yr11 ATAR Accounting and Finance next year and I need a textbook for each unit. There is also a "Course Study Guide" by Kania & Criddle on my book list but it says it is optional -  would anyone suggest getting/not getting it?

Thanks 

Yes definitely. I would suggest that you buy the OT Lee one if it is available. The course guides are great for studying for exams especially. There are practice exams that you will be able to do in those before your exams. Otherwise, you would have to learn all your notes. Try to buy the OT Lee or the one in your book list Have a good holiday