One of the best places to learn more about special libraries is via their associations.

• American Association of Law Libraries (AALL)
  https://www.aallnet.org/
• American Society for Information Science & Technology (ASIST)
  https://www.asist.org/
• Art Libraries Society of North America (ARLIS/NA)
  https://arlisna.org/
• Association for Information and Image Management (AIIM)
  https://www.aiim.org/
• Medical Library Association (MLA)
  https://www.mlanet.org/
• Music Library Association (MLA)
  https://www.musiclibraryassoc.org/default.aspx
• National Association of Government Archives and Records Administrators
  https://www.nagara.org/
• Special Libraries Association (SLA)
  https://www.sla.org/

In addition, you may want to check out these resources.

• Dority, G. K. (2016). Chapter 4, “Nontraditional LIS Career Paths,” Rethinking Information Work: A Career Guide for Librarians and Other Information Professionals, 2d ed. Santa Barbara, Calif.: Libraries Unlimited. Available as an ebook through King Library.
• Lawson, J., J. Kroll, and K. Kowatch (2010). The New Information Professional: Your Guide to Careers in the Digital Age. NY: Neal-Schuman.
• Matarazzo, James M. and Toby Pearlstein, with the assistance of Sylvia James. Special Libraries: A Survival Guide. Libraries Unlimited, 2013. 167p. ISBN1610692670.
• Shumaker, David. The Embedded Librarian: Innovative Strategies for Taking Knowledge Where It’s Needed. Information Today, 2012. 240p. ISBN 1573874526.