This book ring has all the functionality of the other book rings on Thingiverse, but I have closed off the thumb tube so that it doesn't slide down your thumb. I also thinned down the all of the walls as best I could to reduce material usage. Enjoy!
NOTE: You'll have to rotate this 180 degrees in Makerware to have it sit flat on the "non-dome" side. This can be done in Makerware in about five seconds.