Last October a friend told me that Koshigaya, the city I call home, has a nice garden of its own. I'm not entirely sure of the name - it's either Hanata-en or Hanata Dairoku Park.
Koshigaya's garden is small compared to the popular Tokyo gardens, but it's nearby and on a nice day it would be a great place to relax and read a book while sitting on a bench. A bus from Shinkoshigaya/ Minamikoshigaya Station's northern side will get you to the park in about 15 minutes.
Admission is 100 yen and the park hours are 9:00-17:00 April through September (9:00-19:00 Saturday/Sunday/holidays) and 9:00-16:00 October through March.