The Book (or Books) of Enoch is a collection of works purportedly made by Enoch, the great-grandfather of Noach, before the flood. I read that they are not part of the Tanach, even though they contain deep Jewish concepts. How is the book of Enoch viewed in Orthodox Judaism?
3 Enoch is known in Jewish tradition under the name Sefer Hekhaloth. It is part of a wider body of texts known as Hekhaloth literature. This book is now considered one of the primary texts of kabbalah though it is technically, like Sefer Yesirah, pre-kabbalah and subject to interpretations that don't necessitate a kabbalistic metaphysic. At the time it was written, reception to hekhaloth literature in general was mixed. For example, Shiur Qomah, a related text, was first accepted by the Rambam, but then rejected as a Byzantine invention. As for the other two Enochs, there is no evidence they were known or accepted in Judaism, were probably not written in Hebrew, and do not exist in Hebrew translation.