I am actually pretty much in the same boat as you (being an ectomorph). I have to eat a ton of calories in order to gain weight.
First, let me just say not to look a gift horse in the mouth. In other words, there are plenty of people out there who would kill to be able to eat like us ectomorphs and not gain excess body fat. So, just remember to focus on what you do have, instead of focusing on what you don't have.
That being said, I completely understand your interest in putting on muscle. Whether it be to attact potential romantic partners, improve self esteem, improve confidence, etc...or any combination thereof, adding muscle to one's frame is something that I suspect most, if not all ectomorphs aspire to.
However, you should also ask yourself, "Do I just want to look powerful, strong, and athletic? Or, do I actually want to be powerful, strong and athletic?"
If the answer is the former, then there are a multitude of training approaches out there that will help you (to differing degrees) to gain muscle. Mr. Waterbury's articles are some of the most effective in my opinion.
If on the other hand your answer is the former, in other words, you want to be powerful, strong, and athletic first, and muscular second, then I would suggest that you go more towards Gymnastics/Olympic lifting.
Now, I'm not saying that Mr. Waterbury's programs won't make you more powerful, strong, or athletic. I'm sure they will in fact. But, what I am saying is that they are inferior to grymnastics/olympic lifting in that respect.
And honestly, I think that Mr. Waterbury would honestly have to agree with me here. To the best of my knowledge he has never trained elite level gymnasts or olympic lifters. Nor could one hope to compete in such events simply by following his programs.
On the flip side, I have no doubt that a gymnast or olympic lifter could complete Mr. Waterbury's workouts.
But, I degress, I will also say that the athletes following Mr. Waterbury's programs are probably more muscular than most gymnasts/olympic lifters. Although that's not to say that gymnasts/olympic lifters don't build muscle through their trainin. Just look at pictures of gymnasts/olympic lifters and you will see what I mean. Would they win a Mr. Olympia contest? No. But are they skinny? No.
I personally am more interested in form than function, but that's just me. I am simply suggesting that you make sure that you train in a way that will help you achieve the goals that are important to you.
Anyways, I hope that you find what you are looking for and stick with it.