It's probably even better that it doesn't scream "golf related." Online, people are already searching for golf books when they find this on Amazon, so it's not necessary to make it more obvious. And in the book store, the Borders and B&N guys have already been kind enough to group all of the golf books onto one shelf for you, so again, you'll know its a golf book because it's there.
And, it might stand out even better without any green or other typical golf stuff on it.
That's part of it.
People don't have to know it's a golf book in a sea of random books. It should stand out amongst golf books.
On my book shelf, 24 of the 31 golf books on one shelf have green as the dominant color. Several feature clubs, balls, or golfers. Putting greens, fairways, etc. Blech. :)
That's another part of it.
Plus, look at http://analyzrgolf.com/ . I think it's somewhat clear that we kind of lean towards a certain esthetic… :-)
P.S. You can ask a few people… we've literally seen hundreds of designs. Some have been pretty bad. And we're STILL trying variations of these. For example:
No pencil on the spine (probably won't have that regardless of the one we use), an orange-r pencil so it doesn't look quite as much like a #2 pencil, and the right one has a different sized title (compare it to the left one).