There are two things special about Aikido and the dynamic sphere. In the first place the book offers the highly schematic outlook as Abe Sensei used. In the second place it originates from a time where conflict and politics hadnot ruined the aikidoworld as widely as nowerdays.
Noting these two things one can easily understand why it on the one hand is considered a good book by many aikidoka, just because it does not cover politics, on the other hand one can also understand why some dont like it. To them it offers an outlook on aikido from before conflict and technical differentiation.
Others just dont like the colour green