Biochem Book age and suggestions
I would suggest the Lehninger Principles of Biochemistry, which is one of the best in my opinion since it covers most of the key aspects in biochemistry.
It is quite expensive to buy as new, but since it is quite common you can maybe borrow it from a library. In this way you can get an impression about the book and eventually decide if it is worth buying it or not. If you are interested in having it I would buy a secondhand one and I would say it does not matter if it is not the last version, the previous one should be good as well.