should I approach the bible as a guide or a user manual?or should I just treat it as a history book?

The Bible is a guide, a user manual AND a book of history. More important, it is the Word of God from the creator to his created.

Basic
Instructions
Before
Leaving
Earth

As a "history book", it rather stinks.
Civilizations OLDER THAN the alleged date of the Noahic Flood didn't seem to notice that they were completely underwater for a year.

When the Hand of God pushed the Sun BACKWARDS in the sky over a FLAT Earth, as reported in 2nd Kings, ch. 20, nobody else noticed.

When the Strolling Zombies were "seen by many", as reported by whoever made up the Gospel of Matthew, nobody else noticed.
Not even the other three Gospel Writers!

The person who made up Matthew's reports, also claims there was a "Transfiguration", witnessed by John.
But the Gospel of John does not mention it.

The most reasonable attitude SEEMS to be that one should treat it as an anthology of PLAIN fact, EXAGGERATED fact, outright FICTION, some GOOD advice, some BAD advice, some bloody AWFUL advice, a good deal of rip-snorting ADVENTURE, a dash of soft-core PORN, and a few examples of pretty nice POETRY.

Read it to understand the motivations of those who want to others how to live their life. Question anything that gives you pause, and consider why those passages are embraced by those who would try to use such parts to claim "moral power" over others.

Then, considering Jesus's notion of being decent to others, ask what passes the test that that notion implies.

Its ancient superstition and should be seen as such.

The Bible is a book of religion. It is useless as a science text, very poor on history and mathematics and the geography is dodgy in some areas too. If it is the word of a god, it would have to be a very ignorant god.

The Bible is a spiritual guide. If you are not spiritual or if you do not understand spirituality then it is absolutely of no use to you.

The Bible is both a book of history and also a manual for us today, helping guide our lives to be happy and successful in all that we do. 2. Timothy. 3: 16 says "All Scripture is inspired of God and beneficial for teaching, for reproving, for setting things straight, for disciplining in righteousness."

Approach it as a badly written book of historical fiction

The Bible has a lot of history in it all the way from the beginning of creation. But the Bible is a book of instruction on how to serve God.

Both. Someone said that those that do not know history are doomed to repeat it. We should learn from history. The history in the bible is far from impeccable. Still, we can learn from it.