Hm, the Dutch Antroposophical publisher “Christofoor” recommands this book as the essential work of Rudolf Steiner, but I haven’t been able to find an English version of it. When I am correct, the original version is called “Geheimwissenschaft in Umriss”, which is indeed quite a different title. Amazon seems to have over 580 titles of Rudolf Steiner though, so I am sure there is a version of this one among these.
“De Wetenschap Van De Geheimen Der Ziel” encloses a huge amount of subjects, like the character of occult science (Steiner had a scientific approach to the ‘unseen’ world (for most people)), sleep, death, dreams, insight in the higher worlds (and how to get it), development of the kosmos and mankind, astral world, etc., etc., etc.
The book is not spectacularly thick (450 pages), but it actually has a nice length. A good index to use it as reference book.
The writing style of Steiner is not too appealing in my eyes. He gives an awfull lot of details, which he said is needed to understand the whole. For example the chapter about the development of mankind spans many pages and gives detailed descriptions about the forms, conditions and surroundings of mankind from millions years in the past until today. In the beginning this is quite impressive, but after a while it becomes too much.
Also the writing what somebody/-thing would think in a certain situation is rather irritating.
In general this is an extremely interesting book though and gives you most of the basics of Antroposophy and the teachings of Rudolf Steiner.
If you ask me, you better start with the older, but highly acclaimed “Theosophy” (one of my personal favourite books), then this one and then you are ready for the really in depth writings of Steiner.