This is a book that will more than likely fail to impart understanding about operating systems, no matter the background of the reader.
In the preface, the authors describe their goal as "[explaining] a very technical subject in a not- so-technical manner, putting the concepts of operating systems into words that many readers can quickly grasp." A few sentences later, they say "For readers with more technical backgrounds, this text introduces the subject concisely, describing the complexities of operating systems without going into intricate detail." Is it possible to meaningfully describe complexity without going into [intricate] detail? This book is filled with oxymorons and contradictions.
Again from the preface, "To do so, we’ve made some assumptions about our audiences. First, we assume the readers have some familiarity with computing systems. Second, we assume they have a working knowledge of how to use an operating system and how it interacts with them. We recommend (although we don’t require) that readers be familiar with at least one operating system." If a portion of the audience is assumed to have familiarity with operating systems (at what level? as a user? as a computer science student?) why are the authors so determined to avoid going into deeper detail about how OSes work -- if the book is titled, "Understanding Operating Systems"?! And isn't familiarity with OSes synonymous with having basic working knowledge of how to use at least one OS? The verbosity of the preface foreshadows the verbosity found throughout the book - ideas which only require a few sentences to explain are allocated multiple pages of explanations which are difficult to decipher due to the lack of precision in the language and an averseness to going into detail.
There are so many more issues with the book (illogical ordering of explanations when presenting new ideas, chapter bundling of sparsely related topics in what seems to be an attempt to pad book length, outdated technologies (even in 2018) being introduced in the present tense as if they are still in use, no mention of any concepts which first and second year university CS and engineering students should be familiar with from their CS and electronics courses) but unlike some books which are good but flawed -- and for which criticism can be insightful -- this one seems irredeemable. An absolute nightmare to read with hardly anything useful to offer.