Is it forbidden to read useful foreign books due to a transient Waswasa (whispering/insinuation), and is it better to continue reading and disregard the Waswasa, or to abandon it for fear of its return?

You must continue reading beneficial books and not abandon good deeds out of fear of obsessive thoughts (waswas). If obsessive thoughts occur to you, you must strive against them, ignore them, and not yield to them until Allah removes them from you completely and they do not return.