Michael Webster’s sister-in-law probably thought her husband had gotten her a Microsoft Surface Pro 8 tablet for Christmas. That’s what it said on the box. But surface appearances can be deceiving: the contents of the box were shingles, meant to be used on roofs. So the Websters went back to the Boston Best Buy where the gift had been acquired. There, Webster said, they were able to exchange it for another Surface box, which they insisted on opening before purchase. It was also packed with shingles. Best Buy is investigating.