What is the effect of beginning the selection with a summary of
the author's trip to India thus far and then moving to a description
of the Taj Mahal?

The information at the beginning helps the reader decide whether to visit India. By starting with a summary of the trip, the author creates anticipation that encourages the reader to continue reading.

Explanation:

boccaccio employs the voice of his narrator dioneo to represent his ideas on the tension between masculinity and femininity.  while dioneo excites the members of the brigata and recognizes women for their unique skills and independent ideas, he concludes the decameron with a story reminiscent of the society from which these young aristocrats escaped, revealing misogynistic overtones.  dioneo boccaccio is able to explore the gender disparity which is inherent in 14th century florentine society.