The #1 book I'd recommend for any UT player (or any other gamer) is Sun Tzu's The Art Of War. It was written in Chinese 2,500 years ago but it still applies today - and not just for war, but for business and life. But it's especially great for UT.
Some examples:
"To fight and conquer in all your battles is not supreme excellence; supreme excellence consists in breaking the enemy's resistance without fighting."
Translation: If the opportunity is provided, it's
always better to launch. The fact that the other team left a hole open in their defence means that they failed at this next quote...
"To secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by enemy himself."
Translation: Your should always defend by covering every possible attack route. If you're assaulting, you should look for holes that the other team has "provided" to you.
"Victorious warriors win first and then go to war, while defeated warriors go to war first and then seek to win."
Translation: If you're playing a match and the other team picks all the maps, has had more practice, is on a server that gives their team better ping, has more experienced players, and has strategies in place for winning each map, guess who is going to win.
I'm sure the following is true for most of us, but when I'm playing on AS1, I'd say that 70% to 80% of the time, I can tell which team is going to win before the match has ever begun. This is because I usually know the experienced players, and can pretty much see which team is better off. Which brings me to another quote...
"If you know the enemy and you know yourself, you need not fear the result of a hundred battles."
Translation: Why is Bitchy so good at killing me when I'm boarding the ship on Frigate? Is it because she uses her admin hax to find me with radar and shoot homing flak balls with triple damage at me? Well it's partly that, but mostly because she knows all of the 2 or 3 tricks that I like to repeat over and over on that match.
But the same goes for any person/clan. If you know how your enemy fights, and can predict what they're going to do and how they'll do it, you
will beat them. And of course if you're assaulting and you make good use of the first quote, you'll beat them without ever firing a shot.
Translation of this post:
I recommend reading The Art of War.
Specifically James Clavell's translation.
a book thread 
:
)