All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work.
— 2 Timothy 3:16-17 ESV

The Bible is the most relevant book to mankind. No other book will tell you more about who you are, who God is and what God has done throughout history to redeem His creation. The main purpose of biblical teaching is to produce people who glorify and treasure God above all.