I have Covels "Trend Following", and got me into looking at the markets in a structured way.
(one of the earliest trading books I ever bought)
However, it has a generalistic style, with lots of stories and anecdotes, but little real information.
a better read would be Curtis Faiths "Way of the Turtle". It is full of methods of analysing your trades, and the pitfalls of curve-fitting. There seems to be more "real" information in Faiths book than Covels, and thus would recommend Faith over Covel.
The biggest problem with trend-trading is the taking of many, many, small losses, waiting for the big move. Discipline is the key skill here.
The rules can be found freely.