There are different types of companies - public, private, not for profit (non profit or NGO) – and availability of information varies by type.
U.S. Securities and Exchange Commission defines public companies as follows:
“first, the company’s securities trade on public markets; and second, the company discloses certain business and financial information regularly to the public.”
Information on public companies tends to be more easily accessible and a lot of it can be found in their filings with the Securities and Exchange Commission. Analyst reports covering publicly traded companies are also an excellent resource although access is often restricted, and they can only be found in sources that are not available to the public.
Private companies are not required to make their information public; this makes it difficult to find valuable information on them other than what is listed in business directories. Their websites can be an excellent source of valuable information, but there again, what is made available is entirely up to the company. Some do a good job at presenting their products and services and business model in detail; others only offer marketing materials and very basic contact information.
A lot of what is known about private companies might come from press coverage in trade publications or local and national business news.
Please note some of these books might be reference books; reference books are only available for use in the library. You can identify those by looking at the Copies tab in the record of each book – the Location section should say Sherman Library Reference and the Status section should say LIB USE ONLY.