Are brand book and brand guidelines the same or are there any differences?

Allow us to answer it with a quote:

"A brand book is the physical manifestation of the living, breathing concept that is your brand. Without a guiding document, the Brand can spin out into an inconsistent set of representations. In an attempt to slow that process, Marketing Departments often develop Brand usage guidelines.

These guiding documents have a lot of names: Brand Book, Brand Guidelines, Brand Bible, Identity Guidelines, etc, etc, etc. But whatever you call it, the Brand Book helps to define the standard elements of the Brand identity, in an attempt to limit the inconsistency that would otherwise develop as the Brand is implemented and actively used." - Tisha Oehmen.