Grand Canyon Conservancy is the official non-profit partner of Grand Canyon National Park. Their mission is to “Inspire people to protect and enhance Grand Canyon National Park for present and future generations.” This website itself is full of compelling information on Grand Canyon, and they have an online shop where you can find many more books on topics pertinent to Grand Canyon and the Colorado River.
Grand Canyon River Guides (GCRG) is a non-profit organization and a community of river guides and other travelers who care deeply about the Grand Canyon and the Colorado River. GCRG organizes an annual Guide Training Seminar (GTS) to educate new and experienced guides on the most up-to-date Grand Canyon info. Their website includes a library of GTS resources that are available to the public.
For more in depth research, the Grand Canyon Conservancy (formerly Grand Canyon Association), curates an online, searchable Bibliography of the Grand Canyon and Lower Colorado River. This resource is updated regularly and includes in excess of 68,000 books, periodicals, serials, maps, audio-visual works, and electronic media.
This popular website allows guests to rate and post reviews of books from all genres. A search of Grand Canyon related books will provide you with some of the most popular Grand Canyon-related literature and what actual readers thought of each title.