I am sorry to learn of this situation. While in general, a person can view (and or photograph) their neighbor's property from a "lawful" vantagpoint (so if they can stand in their yard and see their neighbor's yard), your neighbor is standing on a ladder to look into your home. This opens a little used tort of "invasion of privacy." (A lot of people try this claim, but rarely have sufficient evidence to support it (again, you can look into your neighbor's yard from a "lawful vantage point" even if it is rude or obtrusive, so many people try this tort without success).
Intrusion of Solitude
Intruding upon another's solitude or private affairs, physically or otherwise, is subject to liability if this intrusion would be considered highly offensive to a reasonable person. This type of invasion of privacy is commonly associated with "peeping Toms," someone illegally intercepting private phone calls, or snooping through someone's private records.
While taking photographs of someone in public would not count, using a long range camera to take photographs of someone inside his or her home would qualify. One or two unsolicited telephone calls may not constitute a privacy invasion, but incessant harassment by calling repeatedly after being asked to stop would. Unlike other forms of invasion of privacy, intrusion of solitude does not require any publication of private facts or images—the act of intrusion alone violates the law.
Example: A man with binoculars regularly climbs a tree in his yard and watches a woman across the street undress through her bathroom window. Her injury is the emotional distress she suffers upon seeing the perpetrator looking at her.
Short of filing a lawsuit, you can try to mediate the dispute with them - contact your local bar association and request referrals to mediators, a third party neutral can often help you reach a mutually agreeable resolution. Use the bar association's referrals to contact a mediator or two, the mediator will then contact the other party to set up a mediation session, and you can go from there - hopefully resulting in a formal or written settlement agreement, and save yourself the time and expense of litigation.