The Netherlands is dense enough that the whole country works as a single trip. Amsterdam, Rotterdam, The Hague and Utrecht sit within an hour of each other by train, and they contrast sharply — canal-ring Amsterdam against Rotterdam's postwar modern architecture, with The Hague's institutions and Utrecht's smaller scale in between.
The guides here cover Amsterdam, Rotterdam, The Hague, Utrecht and a countrywide overview. Bicycles are genuine transport rather than a novelty, and cycle lanes have their own rules that visitors are expected to follow. Two timing notes: the bulb fields bloom roughly from late March to mid-May, which is also when Amsterdam is fullest, and the major museums release timed tickets that sell out on weekends well ahead.