Identifying the kind of a book is the most important of the Questions to ask while reading a book. Answering it already means understanding a good deal of a book. Social science (including psychology and self-help books) are difficult in this regard because it's a random mix of science, philosophy, history, and fiction.
Theoretical books aim to state the truth. Practical books discuss means and purpose, what is "right" and "wrong", what should be done.
Science analyses events outside of everyday reader's experience. Science is experimental, philosophy is "armchair thinking".
Questions of theoretical (speculative) philosophy: being (metaphysics), becoming, cause, and change (philosophy of nature), knowledge (epistemology).
Questions of practical (normative) philosophy: good and bad, right and wrong, duty and responsibility, happiness and the purpose of life, policy and justice, etc. Questions of good life or conduct of individual belong to ethics. Questions of good society and community belong to political philosophy.