Book looks very outdated. Terrible design in regards to font (size mainly) and picture annotations (gets mixed up with actual content). The book is very pre-school looking.
On the positive note, it does provides short and useful tips on DIY CO2 enrichment. It goes into quite a detail of calculating CO2 volume needed.
Conversely, the book is very short and even contains fallacies in regards to humidity and CO2 enrichment. Modern articles show that humidity has to be slightly higher with CO2 enrichment and increased temperatures to have favourable VPD. This book states otherwise. There is no email to bring this issue to them to discuss the reality of it.
Do not use this book as a primary source on the topic. However, it can serve as a supplement.