Gary Renard who wrote Disappearance of the Universe also wrote Your Immortal Self which is also a must read. You really should read Disappearance 1st which is his earlier book but I do prefer Your Immortal Self. Both books help you understand ACIM but nothing can surpass the beauty and truths found in this text (ACIM). I am still making my way through ACIM (have been studying it several years now!) but it has been life changing and rings true with things I have thought since I was a child. It is both very simple and complex - good luck with your studies - I think it's a good idea to quiet yourself before you read and ask for spiritual guidance.