I used Campbell's multi-engine training manual, you know, the one with the dark blue cover that you see everywhere. It's a bit of a slog to get through I'll agree, but it's all in there. Another couple that I found good were the Jeppeson multi-engine training manual (although all the rules and regs. are, of course, FAA) and the relatively recent multi-engine training manual put out by the good Mr. Thom, although not actually written by him. All these are available from the usual outlets. Best of luck and enjoy your course, it's great fun. All I need now is for my flying school to get FTO approval!!!!