This sort of thing, I think. Note that the hierarchy is obvious and only the topmost has a close button. (Clicking to close the topmost would cause the close button in the one behind to be visible, and so on)
download bmml source – Wireframes created with Balsamiq Mockups
I don't see too much of a problem with this, provided that it is obvious what is on top and how to go back down (up?) the hierarchy to the base data. Having only one Close button visible at once helps — and would probably make the tables accessible to screen-readers/keyboards.
In fact I can't emphasise that enough: if it's not clear what the relationship between the tables is, or how to navigate between them, then that does create a problem and the answer must be "It's not a good idea". If it can be made clear, and I don't think I've done a bad job in the mockup, then it's probably workable.
You could make the first and second tables respond to clicks: for example, clicking "Valerie Liberty" in the table here would close the other two windows; but clicking "Library" could simply replace the topmost table with the relevant "sub-data". But that would simply provide shortcuts to closing tables and choosing again.