Israel, The Church and The Bible
After the destruction of the Temple in 70 AD, in order to hold the scattered communities together, the Jews were forced to codify their sacred writings and their laws (council of Jamnia 90 AD). The challenge of Marcion (c150) in Rome (contemporary with the Christian apologist Justin Martyr and the Gnostic leader Valentinius) forced Christianity to define its Scriptural position: Marcion contrasted the God of universal grace proclaimed by Paul with the "petty" God over Israel; the Jewish Scriptures were true but the revelation of an inferior God; the OT was not part of Christian Scripture which comprised Luke and 10 Pauline Epistles shorn of all "Judaizing" OT references. The defence, that Jesus was the Messiah forced Christians to affirm that God spoke through the OT and to define an OT and NT canon. The first was relatively simple as most Christians were Greek speaking and the Septuagint was therefore adopted; but it contained material not adopted by Jamnia and this, known as the Apocrypha, or Deuterocanonical text, was rejected by 16th Century Reformers. It took over 100 years for the NT canon to settle and it was first listed officially in 367. (Incidentally, pace Dan Brown, no attempt was made to suppress apocryphal Gospels, not to be confused with the Apocrypha and other psuedographic writing which circulated freely but whose use gradually died out - KC).
One tragic, salient feature of Christian history is its anti Judaism in spite of Jesus and NT authors being Jews. There was political pressure to transfer responsibility from Rome to the Jews; thousands were massacred during the Crusades and they were increasingly persecuted in Western Europe. In the 19th Century, their 'vengeful' (neo-Marcionite) God was contrasted with the loving Jesus.
Synthesis: The two Testaments are integral and must be read through each other.