For a broader overview of ChromeOS, there are several "Complete Manual" style documents:
: You can download general and model-specific manuals directly from the Acer Support Samsung Galaxy Chromebook Go Go to product viewer dialog for this item. Download File ChromebookCompleteManual4th22.pdf
: The 4th Generation user guide, which covers setup and special keys, can be found on the Lenovo Support portal. HP Chromebooks For a broader overview of ChromeOS, there are
: A complete user manual detailing functions and features is available from AT&T Support Lenovo ThinkPad Chromebook For a broader overview of ChromeOS
If you are looking for a manual for a specific device, manufacturers provide detailed guides in PDF format: Acer Chromebooks