For an overview of an architectural style or information about a notable architect, books and reference resources are a great place to start.
Gale Virtual Reference Library and Oxford Reference have specialized encyclopedic content and topic overviews.
EBOOK Central has an extensive selection of ebooks.
To learn about the evolution of a building, the best resources are primary source documents and visual artifacts like maps, photographs, or blueprints. You can also conduct research about an architectural styles or the architect who designed a building or explore a buildings' context by researching:
Environment, land use, and ecology
This 1995 New York Times Article by Christopher Gray, provides some pointers for researching the history of a NYC building. Pay attention to context and time periods before you begin your research.
Jstor: Digital images of works of art and design, including painting, photography, sculpture and architecture. Images can be downloaded (with some restrictions), printed or saved.
Avery Digital Projects: Includes rare books, architectural drawings and photography, and ephemeral materials from Columbia's Avery Library.
Brooklyn Historical Society Online Image Gallery: A selection of historic images from Brooklyn.
Cities and Buildings Database: Image Collections from the University of Washington.
Laguardia and Wagner Archives: Digital collections include images of NYCHA properties and historic images of queens.
Museum of the City of New York: Digital image collections of New York City. More than 170,000 images available digitally.
Municipal Archives: Selected digitized NYC buildings from tax photograph collections (1930s & 1980s).
NYPL Digital Collections: Streetscapes and Townscapes of Metropolitan New York 1860-1942.
NYPL Fire Insurance, Topographic, and Property Maps / Atlases: Range of locations & time periods. For more recent maps, visit the NYPL map division in person.
City Tech Library has a collection of maps created by the Sanborn Map Company (2000) that show property outlines.
Paper copies of the following are on Reserve in the library -- ask at the Circulation Desk:
Manhattan (between 34-46th Streets and 1st and 2nd Avenues): maps 24, 26, 35-38
Brooklyn: maps 5, 6, 18, 24-25, 28-30, 35
Electronic copies of the following are available in the Multimedia Resource Center:
DWG maps: Brooklyn maps 24, 25, 35
TIF maps: Brooklyn maps 22, 23, 27, 31