I bought this book as I am just starting my course and was looking for some additional reference material to support my studies. The layout and information in this book is great, just what I was looking for. Unfortunately the Unit numbers it covers are limited. The unit numbers it covers are as follows: 301,302,303 and 305 are the mandatory units and 309, 312, 318,322,328 and 329 are the others. They are covered in great detail and are very useful in themselves but if you were looking for any of the others,they are not referenced, although these are apparently the most chosen units.