The Disc Golf Michigan book is an amazing book that covers all of the courses in Michigan.
It’s really detailed and has some great pictures. It has every course in it, with descriptions of the tee pads, if there is a cost, directions, if there are maps, and so on. My father-in-law and I picked it up two weeks ago and put it to instant use. This is the second edition, and was published in 2009, so it should be pretty accurate.
If you want to buy it, visit Disc Golf Michigan to find a store near you, or you can order from there.
I highly recommend it if you want to find new courses.