I'm exactly the same. I tend to get the first book of any series that interests me and read a third before I decide whether to buy it or not. I do buy about 3-4 books a month (mostly epub drm free preferred) plus about 10 european graphic novels (paper books only) a month so I'm a heavy consumer I think.
I follow the newsletter from Borderlands Books in San Francisco. I usually buy one book off their best seller list a month (sometimes I’ll stop in and buy three or four)
I’ve recently started using my local library’s mobile app and I love it. (I typically use this for re-reading or audiobooks for plane trips) I’m tempted to donate my entire bookshelf to the library and let them store and maintain it for me :-p