This has been gathering dust on my shelf for a few years now, and I've only just got round to reading it. The five books of 1st Enoch range from the utterly fascinating to sure-fire cures for insomnia.
Written between the old and new testaments, it gives a fascinating insight into what some Jewish groups believed at that time (for example, several editions of Enoch were found among the Dead Sea Scrolls.)
Anyone with an interest in the New Testament could learn a lot by reading Enoch. Attitudes of people in the gospels have clearly been coloured by the content and even vocabulary of Enoch. And, of course, it's even quoted in Jude and 2 Peter. Parts of it are so startlingly similar to the book of Revelation that it must surely have provided a visual vocabulary for the writer of that book.
For the background and relevance of Enoch, I *highly* recommend "Exploring Jewish Literature of the Second Temple Period" by Larry R Helyer. It provides a great survey of a wide range of this and other books, from the 'Testament of Moses' to Josephus, and from the Dead Sea scrolls to Philo - and much more!