The Bible is one book, not two separate testaments; so the Old Testament is essential for understanding the New.
In this stimulating book on the Old Testament background to Christ, Alec Motyer shows how Jesus is the king expected, who brings in the kingdom looked for in the Old Testament; is both the image and the Word of God; conquers sin and death, and brings the disordered creation to its prefect consummation. To neglect the Old Testament, the author maintains, is to have an impoverished view of the glory of Christ.