And yet you don't realise that the Jewish canon was not closed until the Council of Jamnia in AD 90. Prior to that the Jews and then the Christians used the Septuagint, which guess what, contained these books
Besides, the Samaritans and the Sadducees both kept ONLY the Pentateuch and rejected the books of the Prophets etc. --> so do you reject Isiaih, Ezekiel etc. because it was rejected by these Jews?
Ethiopian Jews -- arguably the oldest untouched form of Jewry use the same canon with these 7 books
Even the earliest Christian books refer to these books:
The Didache (AD 70): "You shall not waver with regard to your decisions [Sir. 1:28]. Do not be someone who stretches out his hands to receive but withdraws them when it comes to giving [Sir. 4:31]"
And there are others, many other references.
RE: the Jewish canon was not closed until the Council of Jamnia in AD 90
http://www.aish.com/jl/h/cc/48939022.html
The Men of the Great Assembly — in Hebrew, Anshei Knesset HaGedolah — was an unusual group of Jewish personalities who assumed the reigns of Jewish leadership between 410 BCE and 310 BCE...
...the Men of the Great Assembly decide which of the multitude of Jewish holy writings should be in the Bible. The Jewish people have produced hundreds of thousands of prophets (both men and women). Which of their writings should be preserved for future generations and which had limited applicability?
The Men of the Great Assembly make this decision and give us what is known as the Hebrew Bible today — or the Tanach. (Tanach is a Hebrew acronym which stands for Torah, Prophets, Writings.)...