If you are a non-scientific or beginner with aquatic plants, this is a terrific reference book for the price. You won't find anything this good for less than 20 bucks. It has excellent pictures so you can ID plants correctly. It has solid info on substrates, co2, and fertilizer. It is the most accurate cheap book on water conditions, ph, buffering, etc.
It also has crystal clear easy to understand explanations of complex things such as photosynthesis and respiration, biogenic decalcification, and iron use. It also has terrific clear info about how to recognize plant problems.
It clearly IDs the most popular species and these are outstanding pictures--much better than those most other and even more expensive books offer. And the writing and diagrams are absolutely fuss-free, clear and plain. A monkey could read this and grow a decent plant!
This will not be particularly useful to an experienced aquatic horticulturalist but it is hands-down the most accurate simple intro level book available.
If you are a botanist or water chemist, you'll be dissappointed, but for the average person trying to grow some decent plants in his or her tank, wow. It's fanatastic! And a great bargain. For 30-40 more you could get great books by Teepot and Walstaad, but this slim volume is essential for the beginner.