Getting started in engraving

[Chance Deus Ex Machina]

Friday afternoon and all the orders were out the door so I thought I would have a bit of a play around.I had a go at carving a skull into a 50p piece as pictured
I started off using a mix match of hand pushers that I had picked up somewhere along the way. This was my first attempt at doing anything like this, and whilst doing it, I kind of started to get a feel of how they should work and be used.However, I noticed they got blunt very quickly and I probably ruined them by attempting to sharpen them.

To finish up, and remove most of the excess I used the cheap power engraver that cousins do. As said, through the process I got that feeling of how it could be done and I am now keen to start exploring and learning how to do it properly.

I was wondering if anyone could recomend some good books about hand engraving and also what tools are a must have ?

regards