The title of your post caught my eye and thus I came running to see what you and others had to say on his name. Not only did he write a lot of books which has changed cannabis cultivation for many years now and done all these amazing things to help pave the legalization of cannabis, but he is also has a legit Ph.D and has written a number of actual scientific articles on a wide range of things and holds a stellar reputation in the scientific community for his work as well outside of cannabis. I am always reminded of his work on the preying mantis, ladybugs, and some others as his research truly opened doors for the world of cultivation and how we address helpful and harmful insect controls. Needless to say I've been a fan of his work for years now, and proudly have a vast majority of his books and know them very well, if I want to quote something from his work I can find the page number with no issue and know which book it came out of. Other cannabis authors seem to drop bread crumbs of information, some of it rooted in facts other things rooted in myths, but not Ed Rothensal he will quote a study so you can do do much research on it to learn even more, he keeps things to the hard cold facts and whether you agree with him or not, his information can be backed up and verified by trusted sources.
When I wanted to go from being a weekend hobbyist gardener to stepping it up to getting serious about growing gardens year around inside and outside the greenhouse told me to use his books as the basis to help me really step up my game on what I really know about plants and everything relating to them. I already had lots of books on gardening, specific plants, horticulture, greenhouse management and so on... so I failed to see why or how a book on growing cannabis was going to help me when I wasn't even growing a single cannabis plant and had no intentions to either. However in reading his first book on Growing Marijuana (the Oaksterdam University Course Book) I was hands down blown away and surprised by how much I actually learned about plants overall and how it changed everything I already knew. Within one year of reading his first book it changed everything for me and it would open my eyes to how much cannabis cultivation is changing the world of even BIG AG and even down to the hobbyist weekend gardeners. That is what brought me to become really serious about studying and researching cannabis cultivation as intently as I have because of how much its changing the way others garden and raise plants.
Overall I can't say a bad thing about Ed Rosenthal, he has had his photo taken with the founder of Fox Farm, Snoop Dog and other big named icons over the years, he is highly respected in both the cannabis community for his years of work and for helping to legalize cannabis for us all. His work is very easy to read and whether he was advising people in the High Times column "Ask Ed" or writing a book he was clear, precise and left you feeling like you actually understood the answer he gave whether you were a new grower without a clue or a long term grower with years of experience. Any time someone tells me they want to learn to grow any kind of a plant be it cannabis or not, I recommend his books as a great starting point, because I know he will cover all the aspects of growing a plant from the soil, lighting, CO2 and everything else; after one book you will know more than you ever would reading 10-gardening books which would never tell you the very basics to growing successfully indoors or out.