Skarik's tips are good, but I would like to add:
Practice and play with your instruments and write music (even short compositions or loops). In synths practice means really exhausting the synth's features so you know what it's composed of and form a sense of its "tonal range", so to speak. While other resources may give you tips about different things that exist in music or describe how a certain technique works, it may or may not help you write your own music and it may or may not help you make something that satisfies you. That I believe is a combination of having the experience to think forward ("I'd like this sound to be like this, so to do it I need to do this or try this.", "This beat sounds a bit too dull/uninteresting, to make it more interesting I could try this." etc.), knowing the tools that you have and having written music and done sounds before.
That's just how I know a synth at least. Dial through the synth's waveform options and all other features and then form a sense of what it sounds like or what sounds it's suitable for and then you'll always know a starting point or a few starting points, when it comes to making a synth sound. Also, studying presets in synths is a great way to see how someone else made a synth sound.
If you really want literature, then this is a pretty interesting book: http://www.synthesizer-cookbook.com/. As is the Computer Music Tutorial by C. Roads.
And this is a good introductory video series, although it doesn't go to much depth into how many ways you really have for shaping a sound (e.g. by adding effects, using a vocoder etc.):
http://www.youtube.com/watch?v=atvtBE6t48M
Also, maybe a bit of a warning:
how to understand music, recreate sounds, create a sound that I imagined, really understand what I'm doing.
Don't get into the mindset of thinking that making music or sounds have certain formal rules or that there's some underlying theory or grammar that explains everything or even something, because as an art it has none of that (apart from e.g. basic music theory that explains notes, scales, chords and rhythm). Fitting into a certain style might include certain "characteristics" that you need to fill in to fit into that style and there might be some good "rules of thumbs", but they are not fixed rules and there might not be words to describe them, nor an actual need to specify them. Many computer musicians and sound producers simply do what sounds right to them and they use the tools as they like (or what they're made for).
