I'd do nothing but reading if I could (ok, maybe eat some great food, buy some fancy shoes between two books...oh, and spend some quality time with the gorgeous guy I married while I am on reading-break anyway...)
Really, really not realistic. Or sexy.
I am not a guy, so I don't know for sure, but I have never met a guy who fought his erections with cold showers. Never once. None of the guys I ever met. Ever.
There are basically two things with most guys: Either it goes down by itself by thinking of something else or they masturbate/have sex and problem is solved after orgasm.
As far as I have heard from males they don't like to stop if they are really aroused because it causes pain. After researching it, there seems to be a physical reason for this (vasoconstriction), so this seems legit (I am glad, that those guys were no filthy liers :-))
So why all these cold showers in novels? Who finds that hot?
If a guy is attracted to a woman/man to a degree that he is physically aroused constantly and without it going away by itself, be a nice romance/erotica author and cut the guy some slack - let him have at least a little solo sex.
End of rant.