To provide a baseline on my perspective, I have no formal education in psychology, psychiatry, or medicine, but I am overeducated in general and I have an immediate family member who has had severe unipolar depression with psychotic episodes for the last 12 years. So I am pretty knowledgeable on psychosis for a layperson, but by no means a mental health professional.
I'll say right off the bat that this book is really going to be of interest to people who have experienced or are experiencing psychotic episodes or disorders, their caregivers, and healthcare professionals, and probably not anyone else. It is a pretty concrete how-to sort of book, not a general background text on psychosis.
This is also a book which is focused on therapy, recovery, and maintaining recovery; it is not a crisis intervention manual. If you have a loved one who is in the psychiatric unit at city hospital on a 72-hour hold because they tried to commit suicide, this is not a book to bring them in the hospital, or for you to read while they're in the hospital. This is more of a book to read after the crisis has passed and the patient is stabilized but not back to functioning as well as they did before the crisis, as part of a program to achieve as full a recovery as possible. In that light, I think it could be quite helpful and is somewhat unique among books on psychosis.
Cognitive therapy basically deals with the linkage between our thoughts and what we do in response to those thoughts, and how all this affects our experience of the world around us. So there is a lot of focus on identifying specifically what you are thinking, how that makes you feel, what you do in response to those feelings, and whether that chain results in outcomes that are positive for you. If the outcomes are not positive, then a big part of cognitive therapy involves identifying ways of changing your thoughts, changing the feelings you experience as a result of your thoughts, and changing the actions you take in response to those feelings, to produce more positive outcomes for your life.
The book provides a set of questions, exercises, and checklists for self-application of cognitive therapy techniques to situations and symptoms common to many psychotic disorders, including paranoia, hearing voices, delusions. etc. It also deals with antipsychotic medications and decisions about continuing or discontinuing their use. There is a chapter specifically advising caregivers, as well.
Each chapter follows a somewhat similar structure, opening with some background on the chapter topic, as well as some "normalizing" information (for example, paranoia is something that everyone experiences, and depending on the situation and degree of the paranoia is not necessarily a psychotic symptom...being afraid to ride the subway at midnight carrying a large sack of cash is a lot different than being afraid to walk down the driveway to the mailbox because you think your mailman wants to kill you).
If you're familiar with "The Feeling Good Handbook" or "A Guide to Rational Living," then the checklists and exercises in "Back to Life" will seem very familiar to you. The key difference is that the two former books provide a set of tools for applying cognitive behavioral therapy for the "average" person experiencing problems which may be stressful and trying (marital problems, anxiety about your job, feelings of inadequacy, mild depression, etc.) but are not necessarily related to any sort of neurobiological disorder (e.g., bipolar disorder, schizophrenia, etc.). This book is a guide to applying these tools for people who are experiencing psychotic episodes. So whereas an example problem from "The Feeling Good Handbook" might be "I don't like to go out in public because I'm extremely overweight and every time people look at me I feel like they're thinking about how fat I am," this book might have an example such as "I don't like to go out in public because every time someone looks at me I believe they are an agent of the sinister government conspiracy against me."
Although the level of the material is pretty accessible to a layperson, if you are approaching it as an absolute beginner you will probably want to supplement it with some general reading on specific mood or thought disorders, since the book really focuses mostly on responding to various symptoms common in psychosis rather than giving a lot of background on mental illnesses.
The book is written by British doctors, which is obvious from the tone and colloquialisms, although I think there is nothing that the average American reader would have issues with. It does, however, mean that some of the specific information about services that are available (such as advance care directives and crisis intervention teams) may not apply in other countries (such as the USA, where procedures and services vary considerably from state to state, and even within states by county or city).