I am using GNU Radio to study digital communications systems.
I have been working on the basic FM receiver with RTL-SDR for a while.

I was trying to find out what is the theory behind the complex I/Q
samples.
What I discovered is that I/Q samples are first related to analytic
signals (the pre envelope) and then to the complex envelope of the
signal
(the complex signal in base band).
In fact, what RTL-SDR outputs to the flow graph is the complex base
band signal, in other words, the signal translated to base band with
just
the positive or negative portion of the spectrum.

Please, can someone with more experience confirm to me if I am correct?
Can someone please recommend me some reference books about the theory of
I/Q samples?

Thanks very much for the help!
I obtained the book (fifth edition) and already read whole section 2.1
(Band pass and Low pass Signals).
That was exactly what I was looking for.

I have one more doubt. Figure 2.1-6 in page 25 shows a real demodulator
(I
attached the figure here).
This is not the same block diagram of the demodulador that we have
inside
Elonics E4000 Tuner (zero-IF demodulador).
We don’t have a Hilbert transformer inside the zero-IF demodulator. We
have
just two paths, one multiplying by cos() and the other by sin().
Perhaps the Hilbert transform is implemented by handling the I and Q
components as a complex number I+jQ inside GNU Radio?
Can someone please explain to me how the zero-IF demodulator is related
to
the real demodulator shown in the book?