How can I understand the phenomenon of mood better? I have been trying to understand the psychology of liking, for example a particular object(human or non-human). But I am unable to proceed with my experiments(I am just an amateur) because I myself discover that I like things at one moment and show no interest in them some other moment in time. Most of the things I see depend also on my mood. So it is this aspect called "mood" upon which I request the community members to throw some light upon.

What is the psychology of mood? Are there any books or mature/good reference materials to understand this phenomenon of mood better?
Are you interested in mood, emotion, or affect? Or all three?

Mood is considered a "diffuse" affective state, whereas emotions are "object specific."  If you're interested in this distinction, look up Mathias Siemer's work.  Gerald Clore also does work on mood.

If you're interested in emotions, then this is a bit harder to tell you who to look up.  There's a vast body of literature on many different things relating to emotions.  If you're interested in pure theory, look up Paul Ekman, Klaus Scherer, and Lisa Feldman Barrett.  If you're interested in emotion regulation, look up James Gross.  If you're interested in positive emotions, look up Barbara Frederickson.  The list goes on!  If you want a not particularly comprehensive overview, you can look at the Handbook of Emotions. 

If you're interested in affect (arousal and valence), look up James Russell. 

Hope this helps.