The majestic public library that stands at the corner of Forty-Second Street and Fifth Avenue in Manhattan is not at its best. For one thing, an edifice that is perhaps the most compelling symbol of this city's free-wheeling, egalitarian intellectual spirit is now known as the Stephen A. Schwarzman building, renamed in 2008 for a Wall Street heavyweight, the billionaire chairman and CEO of the Blackstone Group, in return for a $100-million donation.