That (first) work is the odd-one-out of all his works. There is a marked fork in those interested in his philosophical work and the rest (on the web at least). Notably the first attracts the young philosophers of the masculine persuasion. It might be argued that it is the only work you really need to study if you want to sum up what "spiritual self-realisation" is all about when it boils down to evolving Human Consciousness.... It comes with the usual risk of getting stuck at the head-pole. Hence, Steiner's subsequent efforts to guide onwards and downwards into the heart and limbs.