"Basically, if you purchase these, you would not really need to purchase any other books in the future."
Not true. Some of the information in them is hopelessly outdated, especially the soil stuff. These were written long before the strides made with inorganic soil mixes and even some subsequent black pine techniques. They also don't cover anything but "traditional" mostly Asian tree species. Don't cover collecting or North American native species. They also don't provide accurate, detailed care advice for anyone living outside So. Cal.
If you use these an no other bonsai books, you are living in 1967, possibly 1970-something. Buy them for the excellent design and artistic techniques they go into (like pot selection, more natural shaping, etc) and for their value as icons of American bonsai history written by one of its true pioneers and legends.
They are excellent books, but hardly the only excellent source out there.