Best reading material for multi-engine IR?

[Emkay]

I plan to do a EASA multi engine IR rating in the next couple of years, not to go commercial but to extend the weather conditions and aircraft that I can privately fly.

I still need some more savings so unlikely to happen any time soon, but however I wish to start reading up about it and learning the theory beforehand.

Does anyone have reading material or books to recommend to get me started?

[9 lives]

I find this article very enlightening:

http://www.cfidarren.com/p8740-25.pdf