I am basically in the same boat as you are, although I'm maybe a few months ahead, so I will just give you my experience so far.
First of all, give up hope of a quick understanding. Wittgenstein is difficult, in part because 1) he is going after at some very subtle points, 2) he uses an entirely original approach, and 3) he adopts a stance that is emphatically divorced from mainstream philosophy (if not from the entire Western scholarly tradition). He is difficult also for more banal reasons, such as the fact he wrote in German, and philosophy in translation is invariably problematic, or the fact that (as W himself constantly complained about) many of those who attempt to explain his ideas don't get him at all. (In fact, W says at the beginning of his Philosophical Investigation that his exasperation over seeing his ideas mangled by others was a principal impetus for his writing the book1.)
So far I have found only two secondary sources on W useful.
The first one is Ray Monk's writings on W. His How to read W may be, for some people, the quickest way to get oriented on W. That said, for me reading Monk's thoroughly researched biography of W was indispensable towards beginning to get a clue about W's ideas. Even though this is a biography through-and-through, and a long one to boot (672 p.), W's life was so extraordinary and unusual, and his approach to philosophy and expository style so unconventional, that one almost has no choice but to approach his ideas in this roundabout way, through biography.
The second secondary source I found useful (but only after I had read the two books by Monk) is the entry on W, by Anat Biletzki and Anat Matar, in the Stanford Encyclopedia of Philosophy. I found their summary of the Tractatus (which, BTW, I've never managed to read) particularly illuminating.
Regarding the Tractatus, as I just said, I've never managed to read it, but, more importantly, I don't think I will ever bother to, because it is clear that W came to see the Tractatus as a false start, one that he spent much of the latter part of his philosophical labor tearing down. In fact he is so explicit in his renunciation, not only of the Tractatus, but of the entire philosophical tradition that the Tractatus emerged from, that it amazes me that this work continues to be studied today as much as it is, apparently on its merits as a work of philosophy (and not simply as a historical document, for the light that it may shed on the evolution of W's thought).
I am now reading the Philosophical Investigations, and I'm enjoying it a great deal. I should note that when I first attempted, at a bookstore, to read the first few pages of the PI, I could not make any sense of it at all, and I quickly put the book back on the shelf. Given this initial encounter, I am amazed by how much I am enjoying the book now. The only explanation I can come up with is that doing some preparatory groundwork can make a huge difference.
One last point, since you are in the area of Knowledge Representation, from the little I know from W's work I'd say that his post-Tractatus philosophy is completely antithetical to what I think is mainstream in your area. His take on language (and by extension, on knowledge) seems to me militantly refractory to formalization of any kind. The post-Tractatus W is all about the concrete, the practical you-and-me-here-and-now, and loudly opposed to anything that is "general" and "unified". He wants to conceive of our uses of language and of knowledge as local, "retail" activities, a conception that is inherently antithetical to the high-throughput visions that bring computer science into the picture. You may want to learn of W's ideas for the sake of general culture, and to know what is it that people are talking about (maybe) when they toss his name around, but I doubt that you'll find anything in his writings that you'll be able to actively apply to your work. At most, reading W may convince you of the hopelessness of certain projects, or of certain lines of attack.
1
This, it turns out, was a constant throughout W's career as a philosopher. One learns from his biography that he often despaired from his apparent inability to get his point across. At first I thought this was just some sort of neurosis, but now I'm beginning to think that maybe W had a point after all. For one thing, I have read many comments from many philosophers that very explicitly confess that they don't know what to make of W ("is W for real?", "isn't W grossly overrated?", etc. IIRC, A. C. Grayling is among them, I'm sorry to say; I would avoid his stuff on W if I were you), or who outright call him a "charlatan", etc. [I don't know of any "charlatan" who ever gave away a mind-bogglingly enormous inheritance in his twenties, and lived in great material austerity for the rest of his life. That's just not the "charlatan" phenotype.] But perhaps the most eloquent confirmation of W's sense of being misunderstood is the fact that, even though all throughout the latter part of his career, until the day he died, he was very vocal in his depiction of mainstream philosophy as an utterly misguided pursuit, and even though he very explicitly set out to show, by example, how he thought philosophy should be done, I have yet to find a post-W philosopher who does philosophy in a manner that is anything like the one that W advocated. How can one reconcile this with the fact that W is often described as one of the most important philosophers, if not the most important philosopher, of the 20th century? In light of this otherwise inexplicable state of affairs, I am more inclined to accept that W may have had a point when he complained of not being understood (even by those who say they do). And, as yet another line of evidence in support of this, is the fact that W is often included in the category of "analytic philosophers", even though his post-Tractatus work is an all-out, almost obsessive, assault on analytic philosophy.
