Good resources on branching processes

Question

I'm trying to understand branching processes. Do you know any good and written in a simple way resources / web pages / books.

Free resources are welcome :).

Answer 1

Vladimir Vatutin, Branching Processes and their Applications.

This freely available set of lecture notes by an expert from the field is divided into 15 small chapters. The presentation starts with:

The course of lectures is devoted to branching processes and their applications in queueing theory and biology. It consists of two-level lectures. On Tuesdays we give a relatively non-formal description of the relevant results in branching processes (outlining mainly only the ideas of proofs) and describe possible applications of the formulated results while on Fridays we give technical details and formal proofs for more advanced mathmatical audience. (...)