15hrs is not bad. Thats within normal range. You have to remember. These arent old flip ,phones that can last days without a charge. Most people think the newer smartphones have bad battery life. Which is quite opposite from the truth. I have had a lot of cell phones. Basic, feature, and smart. When smartphones first released the battery was much worse. As technology advanced and got more affordable, more and more people have been switching to smartphones. Those people never saw the technology qradually evolve as they skipped so many generations. These things are running processors, high speed internet, sync facebook, emails, etc... while old phones had a 1" screen and received phone calls. Yes, these phones use up A LOT more power.
10-15 hrs is normal for many smartphones
15+ is pretty darn good as thats getting into a full day. (Considering you sleep)
You are probably putting some good heavy use too since you just got the phone and playing with it.
If the battery life is such an issue, get a phone that offers extended batteries. You wont be happy if it will keep bugging you. Do what you think you can be comfortable with.