Which Book of the Bible is The Red Tent based on? And which Bible can it be found in? Because I was thinking it would be kind of cool to read them in tandem.
Most of the biblical parts come from chapter 34 of Genesis. (And the several chapters before it, too, but that's where the main part of Dina's story comes from.)
As Hil said, what there is of Dinah's story in the Bible is in Genesis, chapter 34. That said, there isn't much. That was Diamant's aim, to flesh it out, in a way that the story made sense to her, and to tell the stories of women who lived at that time. Other than Genesis 34, I think Dinah is only mentioned in Genesis 30 (a mention of her birth), and Genesis 46 (which notes which children Leah bore with Jacob aka Israel). As far as I know, you'll find Genesis first in any Jewish or Christian Bible. If you don't have a Bible, or don't have a translation that strikes you as readable, you can read the Bible online here: [link]
At that site, you can choose the translation (or paraphrase) you prefer. As far as Christian versions of the bible go, The King James Version (KJV on that site) was a literal word-for-word translation and considered accurate for the time. That said, in all those centuries, some English words and expressions have changed meaning, or fallen into disuse, and it's not the most readable. There is a New King James translation as well. I have no experience with it, so I can't tell you, one way or another.
The New International Version (NIV) is, in my mind, a fairly solid modern translation, although it uses a different method than was used with the KJV. The New Living Translation (NLT) and The Message (MSG) are paraphrases. Although I wouldn't recommend for any serious study, they are highly readable for something like this, where what you are looking at is the story.
Jacob's story, which is worth the reading in and of itself, as well as for context for The Red Tent, (incl. his marriages, the fertility of his wives, his religion, his familial history, his sons/Dinah's brothers, etc.) starts in Genesis 25 and continues through Genesis 50. His wives come into it, in chapter 29. The period of time covered from chapters 25-50 is the biblical period which maps to Diamant's story. For those who are unfamiliar, if you want more backstory and have the time, that's what I'd recommend you read.
Dinah's father Jacob, is twin brother of Esau, son of Isaac, and grandson of Abraham. For people who want the further context of the covenental relationship between Israel (the man Jacob became, and the nation itself, because Jacob/Israel is the father of the 12 tribes, as well as the father of Joseph of technicolor dreamcoat fame) and G-d, you might even want to start with Abraham's story (which he starts out as Abram), in Genesis 11.
That said, there's no reason anyone can't discuss the book without reading the parallel chapters in the Bible, because The Red Tent is midrash, or what we might think of as fan fic (but I can't emphasize how beautifully crafted and told this story is). It fleshes out a character who is barely mentioned in the Bible, except for one very action packed chapter. Diamant built her story on historical information available about the women of the times.