This is an especially important text in the body of Whitehead's work. It is the first volume in a "triptych" of works Whitehead produced (the others being "The Concept of Nature" and "The Principle of Relativity") that both established Whitehead as a major philosopher, and laid the epistemological framework of natural science that would become the stepping off place for Whitehead's mature metaphysics.
One of the important aspects of this book is that it is the first attempt in English to found spatial reasoning upon mereological principles rather than set theory. (Lesniewski published a mereological theory as a general foundation for mathematics in 1916. But this was in Polish and was not introduced to the English speaking world until many years later.) Whitehead's motivations are very much in line with William James' notions of "Radical Empiricism": to whit, the full range of experience is the basis of our theories, but this full range includes many relational structures and not just the "sense data" that the Positivists asserted.
Consequently, this book is quite a bit more technical than "Concept of Nature" (which is relatively technical already). However, it presents a radical new and empirically sound theory of nature, abstract reasoning, and science.
This Cosimo edition is particularly welcome for a couple of reasons. First of all, it retains the pagination of the original Cambridge edition, so cross-referencing the two is extremely simple. Moreover, it includes the notes that Whitehead added in the 1924 second edition. This is especially helpful, as that second edition is rather difficult to find and extremely expensive to acquire.
Consequently, this is a valuable addition to any person's library who has an interest in Whitehead's philosophy, or in the philosophy of science. To this latter, Whitehead brings a nuanced understanding of both empiricism and realism to the table that deserves a much wider audience than it has currently received.