They are very useful, I have several of them. The only caution I have though is that I believe they may be printed on demand or printed in small batches, so make sure you look at it when it arrives. I had ordered the G2 one last year and when it came I just opened the box from Amazon and set it aside since things were crazy busy and I never looked at it for a couple months. When I finally did I discovered the pictures were all off in color. My guess is that when mine was printed the ink was running low and by the time I looked at the book it was way too late to return.