Portovenere, Cinque Terre, and the Islands by Michael Turtle
There is some so beautiful about this site - but it obviously suffers from the problem of too much tourism. There is very little authenticity left in the economy of the villages, which now rely almost exclusively on visitors.
However, having said that, I visited in April and was quite lucky with the crowds. Although there were a lot of people around, it wasn't nearly as many as you would get in the peak summer period. And the weather was absolutely perfect for hiking. I would highly recommend people consider going in these shoulder periods.
I found a lot of the visitors just focus on the towns and don't want to do too much hiking. It wasn't overly busy on the trails and I found it really relaxing. As well as doing the main path, I also did some detours so I could see a bit of the agriculture on the hills that are one of the reasons it has been listed.
If it helps, I have put together this guide for hiking Cinque Terre. One of the recommendations I make is to stay in nearby La Spezia and use that as the base to explore - including to Portovenere.