Well it's for that time when you're really just soaking in the tub rather then washing. Just to de-stress, run hot water, sink back, just holding a book up and being careful. Now the shower, that would be a really silly idea... The only time I've gotten a book wet is when the cat decided for some incredibly strange reason to run in and jump onto me while I was in the water..
The trouble is if you really get into a good book, and you realise you've run through most of the book and it's actually about two hours later then you meant it and the really hot water is actually pretty damn cold. I've made that mistake a couple of times.
Hm, DM, by which version of abbreviation are you using? Oh wait, my brain pulled a mental fart there. I have been the games master a few times. The last couple of years my gaming group actually pulled apart due to the trials and travails of life. Work in other cities, marriage and the births of children kind of pull them apart and leave little time for everyone to get time for it. I find I just like to doodle things around just for the mental exercise. And possibly pulling a Walter Mitty....
Edit: Actually the one that freaks me out the most is when people leave a book open and face down so they don't have to search for the page they were reading, and I'm just going "the spine!! put a book mark in and close it!!"