McHeathen said:
All the matter and engery making up the Universe could not up just appeared at a 'singularity' out of nowhere.
Most physicists, in my experience, agree. But there are a wide variety of ideas as to what may potentially replace the singularity, and as yet no evidence to illuminate which, if any, are accurate. A few of the more credible ideas are:
1. The Hartle-Hawking universe (the no-boundary proposal), which treats the whole universe somewhat like the surface of a sphere, so that even though it is finite, there is no singularity.
2. Loop Quantum Cosmology. Some physicists are taking a speculative proposal for quantum gravity, loop quantum gravity, and applying it to a collapsing universe. Their calculations seem to indicate that such a collapsing universe should "bounce", producing one like our own.
3. Some theorists have proposed a universe where the "equilibrium" state is a state with a small but positive cosmological constant, where new "universes" are born out of the vacuum of others all the time. Sean Carroll and Jennifer Chen proposed one idea (which is an infinite universe). Andreas Albrecht has proposed a similar but distinct idea ("de Sitter equilibrium cosmology").
Unfortunately I'm not entirely sure about any popular books on this subject. It is, after all, quite hypothetical at this point, without evidence to show the way. All we have are ideas, and all of them could be wrong.