I've always worked on the principle that if, when I first see something, I think I might enjoy it then get it - I might not see it again and/or it may never be reprinted. My definite point tends to be a negative rather than a positive, if I don't think I'll read it, if it's something I have no interest in or feels like rubbish then I don't bother. Means that I probably have far more than I'll ever be able to read but you can never have too many books...
