When personal computers began infiltrating private homes, some soothsayers predicted one result would be the decline of public libraries. It hasn't happened, at least not in the Twin Cities area where libraries are booming: they are serving more patrons, buying more materials, renovating buildings, and exploring new ways to pay for it all. Peter Pearson, who directs the advocacy group "Friends of the Saint Paul Public Library," remembers the dark days of the 1980's when city budget cuts hit the library system hard.