Its very likely that it was. Our modern version is questionable though.
The modern version of Enoch that we have came from Ethiopia. In translation it may be a copy of a copy, although the Ethiopian church says the whole thing actually originated in the Ethiopian language:
The traditional belief of the Ethiopic Orthodox Church, which sees 1
Enoch as an inspired document, is that the Ethiopic text is the
original one, written by Enoch himself. They believe that the
following opening sentence of Enoch is the first and oldest sentence
written in any human language, since Enoch was the first to write
"ቃለ፡ በረከት፡ ዘሄኖክ፡ ዘከመ፡ ባረከ፡ ኅሩያነ፡ ወጻድቃነ፡ እለ፡ ሀለዉ፡ ይኩኑ"
"በዕለተ፡ ምንዳቤ፡ ለአሰስሎ፡ ኵሉ፡ እኩያን፡ ወረሲዓን።"
"Qāla barakat za-Hēnōk za-kama bāraka ḫərūyāna wa-ṣādəqāna 'əlla hallawu yəkūnū ba-ʿəlata məndābē la-'asassəlō kʷəllū 'əkūyān
"Word of blessing of Henok, wherewith he blessed the chosen and righteous who would be alive in the day of tribulation for the removal
of all wrongdoers and backsliders."
Doctrinally its hard to match to the scriptures, but again this could be the result of translating a work from one language that was translated from yet another language.
There is also the question of insertions. For instance the book flows fairly well, but then a deviation is made to a strange story about Noah which differs in both delivery and believability. There are a few like this.
Enoch is a very advanced book, far beyond Revelation, layers deep in prophesy. Its quite hard to approach without questioning modern understanding of scripture, so it must be approached carefully.