I've never heard of an exception where a society refused to answer questions about the contents of their collections, even though they might not necessarily allow general access to rare and fragile materials for fear of damage. These provide important ways for members to communicate information. A society may, for example, publish all or part of its work on transcribing court minutes. State and local societies publish articles that help describe their area in different historic eras. From these articles, you can better understand the conditions in which your ancestors lived or what caused them to move to or from that area.
Some societies publish the results of their projects.
Most of these books never find their way to the bookstores. You must make contact with the society to learn of their activities and their publications. This year's conference in Denver, CO, from May 6-9, offers scores of lectures by experts in many areas of the genealogy field. It also hosts a huge collection of vendors selling books, software, CD-ROM's, forms, and all sorts of paraphernalia. The societies also announce upcoming events, performing a valuable service to members by keeping them apprised of other organizations' activities.