Yes it is the only direct revelation we have. Another but indirect way of knowing about God is through His work in creation. See Romans 1 and Psalm 8 and Psalm 19.
Here are some links to useful information
The Divine Origin of the Bible: www.thisisyourbible.com/library/show/160
The Miracle of the Bible: www.thisisyourbible.com/library/show/149
Getting to Know God: www.thisisyourbible.com/library/show/165
I hope you have found this helpful.
God bless you,