As you go through life the secret of the Universal Law of Attraction (LOA)may be hiding in plain sight, until it tumbles into your awareness as it did into mine about two years ago.
In my case the Huna Philosophy, with its seven principles, including the world is what you think it is, and Energy Flows where attention goes opened the door. The Law of Attraction nestles within the teachings of wisdom masters such as the Buddha -All that we are arises from all that we have thought. The mind is everything. What we think we become. With our thoughts we make the world.
Then there is Mark 11:24. Whatever ye desire, ask for it, believe that ye have it, and it shall be yours. The book and movie The Secret uses the Ask, Believe, Receive concept, though without acknowledging its not so secret origin. Imagine you already have it. Imagination, feelings, decisions/actions = results.
This book gets my highest recommendation as the most user friendly book I have read on the topic. You can read this book in hours. The book contains easy to complete worksheets, so you can apply the principles immediately, whether it is to relationships, wealth, career.
In addition, the author is an NLP (Neuro Linguistic Programming) practitioner, so he demonstrates excellently how to change emotional states from negative to positive, simply by asking a question. Negative states and thoughts are not resourceful in consciously using the Law of Attraction.
Have you ever noticed that you seem to attract similar relationships? He explains how to stop continually attracting relationships we do not want, and get what we want instead. Its amazingly simple, and had me going duh, because until I read this book I made this very common mistake. No other book I have read covers this issue, and it is so important.
Furthermore he demonstrates common limiting beliefs, how to overcome limiting beliefs and resistance, to assist in the allowing process.
Like attracts like, and feelings are important, so if you feel bad, you attract bad situations, and feeling good attracts more good. So, it is important to feel good about whatever you wish to attract into your life, otherwise it will not manifest.
This book is remarkably consistent with the movie, and book THE SECRET, yet is far more detailed on how to apply the principles. Other books I recommend are Ask and it is Given by Esther and Jerry Hicks which uses the emotional guidance system, and Secret of the Ages by Robert Collier, and the works of Sanaya Roman, a metaphysical writer.
If you want a spiritual book on the topic, check out Florence Scovel Shinn. LOA is definitely a must have book on this topic. I hope this was helpful.