What is the theme of the "Far from the Madding Crowd"?

Some of the themes in “Far From the Madding Crowd” are unrequited love, the social caste system, and tragedy.  The biggest part of the novel is about Gabriel being in love with Bathsheba.  Through his tragedy of losing the farm, and her good fortune of inheriting the farm from her uncle they become socially unacceptable as a couple.  He is too poor and she is too rich for the union he so badly desires. 
The themes of the novel are evident from the first few chapters.  Once Gabe has lost his farm, he is “free to wander anywhere in search of work, but he heads to Weatherbury because it is in the direction that Bathsheba has gone. This move leads to Oak’s employment at Bathsheba’s farm, where he patiently consoles her in her troubles and supports her in tending the farm, with no sign he will ever have his love returned.”  Then there is the complication of Boldwood’s feelings for Bathsheba. “Bathsheba herself suffers a similar unrequited love for Sergeant Troy. She feels he is mistreating her once they are married, but she cannot help herself because she loves him so much. …When they argue trip he plans to take to see Fanny, and Bathsheba regrets how much she used to love him, Troy can only mutter, “I can’t help how things fall out . . . upon my heart, women will be the death of me.” When he is thought to have drowned, though, Bathsheba still thinks enough of him to go on waiting, to see if he will come back. “