This is a great little book that I purchased when I decided that I wanted to get into keeping a marine aquarium - it is definitely a good book for the beginner, and probably a good reference book for the more experienced hobbyist.
The book is well written with easy to understand language that won't confuse the inexperienced beginner. It is also well structured; it begins with basic equipment and aquarium setup, before moving onto introducing livestock etc. to your aquarium. The book also progresses in a logical way, listing fish and creatures generally in increasing difficulty of maintenance.
The book also provides sufficient depth on each fish's behaviour, temperament and typical characteristics etc. Further to this, it is illustrated with beautiful photographs that keep it interesting and helpful.
In conclusion, this little book is great value for money and has an excellent amount of information supported by a lot of brilliant photos and illustrations. In saying that, it is most likely aimed at beginners more than an experienced hobbyist, but I believe it is still sufficiently cheap that experienced hobbyists should purchase this as a quick reference book.