No, it is not obsolete. there is a lot of wisdom to be found. Proverbs would be difficult to replace. The stories of the OT are rich and the personalities colorful.
Having said this, there is much that is worse than simply obsolete in the OT. The Historical books credit God with planning the massacres of tens of thousands, or even more, people. Horrendous things were done in the name of God. This has given religious leaders in later times a faulty pattern to follow. Here we are in the 21st century, still fighting Holy Wars; still saying it is God's will for us to kill our neighbor.
Not obsolete. It is a big book and there is a great deal to gain by reading it. But beware what you learn in select places. Read with brain in gear and Reason seated firmly in her place.