If I were going to recommend the basic Michael books to have, I would most definitely start with the Tao to Earth and Earth To Tao books by Jose Stevens. I've had mine so long and read them so many times they are literally falling apart at the seams, but I still get some new understanding out of them every time I read them.
For something much different in organization, but very packed with information, I would also recommend Shepherd Hoodwin's The Journey of Your Soul. It's mostly written from Shepherd's perspective with some channeled sections here and there, and this dual-perspective gives huge amounts of useful information about the teachings. There are even some bonus comedy sections at the end -- I'll never forget the old soul hot tub!
Those two together give a pretty good grounding in the teachings.
And as a bonus, a great book that is less about learning the system and more of a how-to manual for living a better life Michael-style is Searching for Light by Carol Heideman. Absolutely love this book, particularly the visualization Michael gives of what our world will be like in the future. Just wonderful.
