When Rees wrote this book, he (probably) still was a member of a lodge working under the United Grand Lodge of England. Later he would leave it for a lodge under the British federation of Le Droit Humain. The reason for this is that Rees found that UGLE has lost the esotericism of Freemasonry that he did find within Le Droit Humain.
I wouldn’t call this “handbook for Freemasons” “esoteric”, but the author certainly leaves the purely moralistic approach to Masonic symbolism way behind. Rees’ approach is more more spiritual, even leaning towards religious with his many references to ‘reaching towards God’ and the like.
The book mostly seems to aim at the newly made Entered Apprentice, Fellow Craft and Master Mason. He tells the reader what has just happened to him (her), speaking about the rituals in detail, giving explanations and most of all, put elements in a context. Of course the book is based on the rituals that he worked him at the time of writing, so details may differ from your own experiences. It is quite likely that your rituals will be different from those described in the book.
Of course, roughly speaking, things will be similar, or at least comparable or understandable, and Rees certainly has some interesting suggestions for approaches to certain elements of the rituals, so just because your rituals may differ, should not withhold you from reading the book.
From the above you may have understood that this is a book for Freemasons. When you are still considering joining, do not yet read this book. Not that you are going to find passwords, signs or steps in this book, but you will know too much of the proceedings to be surprised when you are subject to them yourself and surprise is an important element of undergoing the rituals. According to the author, the non-Mason is better off with “The Stairway Of Freemasonry“.
2006 Lewis Masonic, isbn 9780853182535