Ah yes very good points, Magus. I am in much the same opinion as well, as such a new religion as Wicca is always changing to the point where one wonders about validity. For a system to work, there needs to be at least some form of constancy or pattern involved. When people follow a feeling, and not a set of guidelines as in more organized religion, things can get lost and cluttered along the way.
The book actually does mention, being written by a modern Druid, that much was lost due to conquerors and nonbelievers. The Romans and such. But the author does her best in a very basic but detailed manner to compile what IS known (such as the Gods, who were mostly recovered) and to eliminate fluffiness. Whether you consider yourself a Druid, or Wiccan, it is from what I have seen, written in a very similar outlook. A good and intriguing read, nonetheless. Also, yes I have met these very... odd, Druids. But I assure you she is VERY down to Earth in her teachings.