I find the dark chocolate a little too rich for my taste too, so I substitute it for milk chocolate and it tastes delicious! You don't use a super thick layer anyway so the taste is not overpowering.
Planet Cake's website is: planetcake.com.au. The book is called Planet Cake - A beginner's guide to decorating incredible cakes. If you get it through the Book Depository you can get free postage - just remember it's all metric measurements.
If you want to pair up the ganache with a delicious cake, I suggest you try this one: http://www.cakesandmore.org/blog/category/recipes/
It's the Cherry Ripe Mud Cake. There's also the Planet Cake ganache recipe on this page too.