Brooklyn is New York's most populated borough with over 2.6 million residents.  The lack of traditional tourist attractions (Times Square, Central Park, etc.) make this an ideal area to see how real New Yorker's live.  This can mean watching young professionals get plastered in Williamsburg on weekend afternoon, relaxing in Prospect Park, or even shopping at a Costco in Sunset Park.  During the summer Coney Island and Brighton Beach offers an escape from the city but not the crowds.

One Brooklyn's most defining feature is the Brownstone - a series of rowhomes using a brown stand stone for the outside facade.  Most of the homes have stairs leading up to the main floor.  The single family homes have now been subdivided into smaller units.  
PROSPECT  PARK  AND  PARK  SLOPE
Frederick Olmstead and Calvert Vaux designed both Central Park and Prospect Park.  While Central Park receives all the attention the designers considered Prospect Park as their preferred park.  I'm not so sure about that.  I've walked through the park twice and while it's a nice green space...it's not Central Park.  To the west of Prospect Park is Park Slope one of New York's nicest residential areas.
Park Slope's main commercial thoroughfare is 7th Avenue from 9th Street to 15th Street.  Aside from a few restaurants the stretch seemed old and dated.  The local coffee shop, Cusp, was underwhelming.  The brownstones in the surrounding area are the real attraction.
PUERTO  RICANS,  CHINESE,  AND  HASIDIC  JEWS
New York is a melting pot of cultures...kind of.  Walking around Brooklyn's Sunset Park neighborhood you will see Puerto Ricans, Chinese, and Hasidic Jews.  You think how wonderful they can all live together.  Then you will notice that with a few commercial exceptions they tend to all live in their own separate world.  The Puerto Rico's dominate 5th Avenue.  The Chinese 8th Avenue.  The Hasidic Jews side streets in between.  There are streets you can walk down where every resident seems to be a Hasidic Jew.  On Columbus Day the Hasidic Jew School Buses pick up students.
I'm not sure of the connection but Hasidic Jews...the water...on a Sunday just seem to go together.  Whether it was at waterfront in Sheepshead Bay or a dock near the Brooklyn Army Terminal, where there was water, there were Hasidic Jews reading the bible.
At the southern end of 5th Avenue between 59th and 60th Streets sits the Basilica of Our Lady of Perpetual Help.  It's a glorious Catholic Cathedral who's congregation reflects the areas changing demographics.
​I’m sure that if your goal for visiting Coney Island is to ride the amusement park roller coaster and sit on the beach, that summer is a better time to visit.  If your goal is to enjoy the neighborhood and boardwalk in peace and quiet, visiting on a Friday in September can’t be beat.  I had the boardwalk to myself. 
 There’s great artwork accompany the rides. 
There’s also no lines a Nathan’s—which is good because the hotdogs are not exactly worth waiting in line for.