Training books

[Furberger]

I'm a fairly keen cyclist, do a bit of cross country, a few duathlons, ride a bit of DH, compete at the velodrome, do some road miles and do a bit of touring. Bit of everything. I'm reasonably fit and reasonably quick but nothing special. I've realised that although I cover a decent number of miles a week, I don't specifically train, I just ride when I want to.
Next season I want to take it up a notch and actually become competitive rather than just an also ran. I need to develop a training plan over the winter, stick to it and measure some improvement.
Bearing in mind the broad range of disciplines I'm involved in, can anyone give me some pointers, a training plan or recommend a good book that will enable me to improve my fitness?
Cheers.