Barbara Mercer wrote in from McKinney, Texas to tell me she was invited to her first engagement party and she wasn't sure if she needed to take a gift. Its a great question!
Technically (according to Emily Post) you do not need to take a gift to an engagement party but more and more people are doing so these days.
It used to be that an engagement party was more of an announcement party. The parents of the Bride or Groom would host what would look like a typical cocktail or dinner party and then announce, after all of the guests had arrived, that the couple was engaged. Of course, now this type of announcement is typically done on FaceBook and word travels too fast to make a surprise announcement.
It is certainly not "bad etiquette" to take a gift to an engagement party but do keep in mind that you will have opportunities to shower the Bride and Groom with gifts throughout their engagement period and again at their wedding.
If you really want to take something, I suggest that you take something thoughtful such as personalized stationery (they will have a lot of notes to write in the coming months) or sentimental. Many brides have not yet registered for the gifts they want so you will need to use your imagination and come up with something meaningful. Of course, my book, The Wedding Workbook: A Time Saving Guide for the Busy Bride, would make a great engagement gift too! ;-)
If the Bride has read an etiquette book she will be sure to open the gifts that are brought to her engagement party AFTER her guests have left and write notes of gratitude within the following two weeks.
I hope this helps Barbara! Have fun at the engagement party!