Boettner is in a sense a popularizer -- he will present a condensed version of the views of those theologians whom Ruben mentioned. Boettner was not an originator or "original thinker" in that sense.
He did play a crucial role in the period between 1930-1960, for his works were some of the few books to be found that presented the Reformed view, yet were readily accessible by the intelligent layman.
Boettner was very much a bridge from Old Princeton to the present day situation. Without him, Machen, and a few others, there was quite a dearth of good solid material available in that era.