Salamualaikum brothers,

The question posed is; is the hadeeth and sunn'ah books from Allah or people's minds.

This is a very interesting question, before I answer it im going to have to explain to you the definitions of the terms; Hadeeth and Sunn'ah.
The sunn'ah is what the prophet (PBUH)did in his every day life, that we muslims try our best to follow. Because prophet mohammad (PBUH) was the best man who ever took a step on earth, we try our best to follow each of the things he did in his blessed lifetime.

Hadeeth, is a collection of recorded data that people have recorded the prophet (PBUH) saying. There are two types of Hadeeth,
Authentic hadeeth,
Common hadeeth, (this is what i call it)

Authentic hadeeths are teachings and rules in islam that the prophet had said, and everyone gave witness that this was true. These hadeeths are called authentic hadeeth. Example; sahi al bukhari,

Common hadeeth are hadeeths that muslims claim the prophet had said and there is either little or no witness to prove it. However muslims follow these hadeeths as long as it does not conflict with the teachings of the Quran, Authentic hadeeth. or the shariah.

Inshalah my post was beneficial to you.
Remember Allah knows best

Peace be upon you brothers
Omari